Note: Descriptions are shown in the official language in which they were submitted.
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COMPOUNDS AND METHODS
FIELD OF THE INVENTION
This application (Serial No. 08/738,379, filed October 25, 1996) is a
continuation-in-part application of Serial No. 08/663, l48, filed June 12,
1996, which
is a continuation-in-part application of International Application
PCT/LJS94/144I4,
filed December I5, 1994, which claims priority from Serial No. 08/235,624,
filed
April 29, 1994, and GB 9325621.2, filed December 15, 1993. This invention
relates
to libraries of non-peptide compounds each comprised of a core structure and
methods for making such libraries. This invention also relates to novel
silicon-based
polymer resins and silane linkers, methods for their preparation and their use
in the
synthesis of libraries of aromatic carbocycles to be screened as
pharmaceutical
agents.
BACKGROUND OF THE INVENTION
In the continuing search for new chemical moieties that can effectively
modulate a variety of biological processes, the standard method for conducting
a
search is to screen a variety of pre-existing chemical moieties, for example,
naturally
occurring compounds or compounds which exist in synthetic libraries or
databanks.
The biological activity of the pre-existing chemical moieties is determined by
applying the moieties to an assay which has been designed to test a particular
property of the chemical moiety being screened, for example, a receptor
binding
assay which tests the ability of the moiety to bind to a particular receptor
site.
In an effort to reduce the time and expense involved in screening a large
number of randomly chosen compounds for biological activity, several
developments have been made to provide libraries of compounds for the
discovery
of lead compounds. The chemical generation of molecular diversity has become a
major tool in the search for novel lead structures. Currently, the known
methods for
chemically generating large numbers of molecularly diverse compounds generally
involve the use of solid phase synthesis, in particular to synthesize and
identify
peptides and peptide libraries. See, for example, Lebl et al., Int. J. Pept.
Prot. Res.,
41, p. 201 ( 1993) which discloses methodologies providing selectively
cleavable
linkers between peptide and resin such that a certain amount of peptide can be
liberated from the resin and assayed in soluble form while some of the peptide
still
remains attached to the resin, where it can be sequenced; Lam et al., Nature,
354, p.
82 ( 1991 ) and (WO 92I00091 ) which disclose a method of synthesis of linear
peptides on a solid support such as polystyrene or polyacrylamide resin;
Geysen et
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al., J. Immunol. Meth., I02, p. 259 ( 1987) which discloses the synthesis of
peptides
on derivatized polystyrene pins which are arranged on a block in such a way
that
they correspond to the arrangement of wells in a 9b-well micratiter plate; and
Houghten et al., Nature, 354, p. 84 ( 1991 } and WO 92I09300 which disclose an
approach to de novo determination of antibody or receptor binding sequences
involving soluble peptide pools.
The major drawback, aside from technical considerations, with all of these
methods for lead generation is the quality of the lead. Linear peptides
historically
have represented relatively poor leads for pharmaceutical design. In
particular, there
is no rational strategy for conversion of a linear peptide into a non-peptide
lead. As
noted above) one must resort to screening large databanks of compounds) with
each
compound being tested individually, in order to determine non-peptide leads
for
peptide receptors.
It is known that a wide variety of organic reactions can be carried out on
substrates immobilized on resins. These include, in addition to peptide
synthesis
reactions which are well known to those of ordinary skill in the art,
nucleophiiic
displacements on benzylic halides, halogenation, nitration, sulfonation,
oxidation)
hydrolysis, acid chloride formation, Friedel-Crafts reactions, reduction with
LiAlH4)
metallation, and reaction of the organometallic polymer with a wide variety of
reagents. See) for example, N. K. Mathur et al., Polymers as Aids in Organic
Chemistry, Academic Press, New York, p. 18 ( 1980). In addition, Farrall et
al., J.
Org. Chem., 41, p. 3877 (1976) describe the experimental details of some of
these
reactions carried out with resins.
The above-mentioned known organic reactions when applied to solid phase
synthesis using known polymeric resins, yield non-peptide compounds containing
auxiliary functional groups such as carboxyl, phenolic hydroxyl, amine, amide
or
bulky groups, all of which have their own unique pharmacological properties. A
hydrogen atom offers its own unique pharmacological properties. However,
currently) there exists no solid phase synthetic resin linker directly bonded
to a
carbon atom of a compound) which, upon cleavage of the compound from the
resin,
yields a compound with a hydrogen on the carbon at the cleavage position. See,
for
example, Bunin, B.A. & Ellman J.A., JACS,114, pp. 10997-10998 (1992}, which
reports the solid-phase synthesis of 1,4-benzodiazepine derivatives. Unlike
the
instant invention, that method is limited by requisite introduction of
auxiliary
functionality, e.g., carboxylic acid, in the target molecule in order to
facilitate
attachment to the solid support. Furthermore, no apparatus or method for
multiple,
simultaneous synthesis is described by Bunin & Ellman.
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It has now been discovered, as disclosed herein, that silicon-based polymer
resins are useful in the preparation of a single compound, e.g., an aromatic
carbocycle, or a library of molecularly diverse compounds which are aromatic
carbocycles, each comprising an aromatic carbon atom and at least one
substituent
that is not hydrogen or alkyl, said aromatic carbons having a hydrogen,
halogen,
hydroxy or acyloxy group bound to them after cleavage from the resin.
It has also been discovered that certain non-peptide compounds, each
comprised of a core structure, bind to a variety of receptors, in particular,
G-protein
coupled receptors. It has further been discovered that the core structures,
including
aromatic carbocycles, may be used as templates for developing libraries of non-
peptide compounds which are analogs of the core structures. Therefore, rather
than
synthesizing individual analogs of these non-peptide compounds for screening,
large
numbers of non-peptide compounds which may be receptor ligands, in particular
G-
protein coupled receptor ligands, can be synthesized by the combinatorial
methods
described herein and screened in assays developed for determining lead
compounds
as pharmaceutical agents. The methods disclosed herein may also be applied to
obtain libraries of compounds, including aromatci carbocycles, that are enzyme
inhibitors, receptor ligands or channel blockers.
The current methods for generation of lead compounds have a variety of
limitations, therefore) demonstrating the necessity for new methods for
generating
and determining lead compounds as pharmaceutical agents.
SUMMARY OF THE INVENTION
The present invention is directed to non-peptide compounds, each comprised
of a core structure. The present invention is also directed to the use of
these core
structures as templates for developing libraries of non-peptide compounds
which are
analogs of the core structures. Further, this invention is directed to
libraries of
compounds which comprise receptor ligands, in particular, G-protein coupled
receptor ligands, enzyme inhibitors and channel blockers and the combinatorial
synthetic methods for making such libraries of compounds. Still further this
invention relates to novel silicon-based polymer resins, methods for preparing
said
resins and intermediates used in the preparation of said resins. In this
regard, one
aspect of this invention relates to methods for preparing one or a plurality
of
derivatized compounds by resin-bound synthesis, wherein the compounds are
aromatic carbocycles each comprising an aromatic carbon atom and at least one
substituent X, A, B or C that is not hydrogen or alkyl, said aromatic carbons
having
a hydrogen, halogen, hydroxy or acyloxy group bound to them after cleavage
from
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the resin. In particular, this aspect of the invention relates to methods for
utilizing
silicon chemistry to effectuate the cleavage of an aromatic carbocycle from a
polymer resin while leaving a hydrogen, halogen, hydroxy or acyloxy group on
the
aromatic carbocycle at the cleavage position. Yet further, the present
invention is
directed to methods for screening a compound or plurality of compounds made
according to the synthetic methods disclosed herein, which comprise using the
compounds in suitable assays developed for detecting the compounds' utility as
pharmaceutical agents. In addition, this invention relates to a method of
screening
G-protein coupled receptors with ligands that are known to bind other G-
protein
coupled receptors, or that are related to ligands that are known to bind other
G-
protein coupled receptors.
DETAILED DESCRIPTION OF THE INVENTION
The term "core structure(s)" is used herein at all occurrences to mean a core
molecular structures) which is derived from compounds which have been shown to
interact with a receptor) in particular, a G-protein coupled receptor, and
which is
used as a template for designing the libraries of compounds to be made. Core
structures may be aromatic carbocycles as defined below.
The term "library of compounds" is used herein at all occurrences to mean a
series or plurality of compounds derivatized from their core structure.
Suitably, the
core structure used for designing a library of compounds is an aromatic
carbocycle.
The term "combinatorial library" is used herein at all occurrences to mean a
collection of compounds based upon a core structure, for example, an aromatic
carbocycle structure, wherein the library contains a discrete number of
independently variable substituents, functional groups or structural elements,
and
further, wherein the library is designed so that, for the range of chemical
moieties
selected for each of the independently variable substituents, compounds
containing
all possible permutations of those substituents will be present in the
library. Thus,
by way of illustration, if a core structure, labeled R, contains three
independently
variable substituents, labeled X, Y and Z, and if X is taken from m different
chemical moieties, Y from n different chemical moieties and Z from p different
chemical moieties (wherein m, n and p are integers which define the size of
the
library, and which range between 1 to 1000; preferably between 1 to 100; most
preferably between 1 to 20)) then the library would contain m x n x p
different
chemical compounds and all possible combinations of X, Y and Z would be
present
on the core structure R within that library. The methods for preparing
combinatorial
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libraries of compounds are such that the molecularly diverse compound members
of
the libraries are synthesized simultaneously.
The term "aromatic carbocycle" is used herein at all occurrences to mean a
compound which comprises a single ring or a fused ring system, preferably 5-14
membered ring systems, and, for purposes herein, includes an optionally
substituted
biphenyl, composed of carbon atoms having aromatic character, e.g.,
characterized
by delocalized electron resonance and the ability to sustain a ring current
and which
ring or ring systems may include one or more heteroatoms selected from oxygen,
nitrogen or sulfur. The aromatic carbocycle may be optionally substituted by
one or
more substituents herein described as "substituent X") "substituent A",
"substituent
B" or "substituent C". When the aromatic carbocycle is a biphenyl, the
substituents
X, A, B or C may be) independently, on one or both rings. This is similarly so
for
other aromatic carbocyclic rings or ring systems as defined above. It will be
recognized by the skilled artisan that a large number of aromatic carbocycles
may be
made using the silane linkers of this invention, provided that the chemistry
used to
prepare the aromatic carbocycles is compatible with the aryl silane bond,
defined
below. Suitable aromatic carbocycles include) but are not limited to,
optionally
substituted phenyl rings) optionally substituted naphthyl rings, optionally
substituted
tetrahydronaphthyl rings, optionally substituted anthracenyl rings, optionally
substituted 1-) 2- or 3- tetrahydrobenzazepines; optionally substituted 1,4-)
1,5-) or
2,4- tetrahydrobenzodiazepines; optionally substituted biphenyl tetrazoles;
optionally substituted 1,3- or 1,4-diaminobenzene compounds; or optionally
substituted 1,3- or 1,4-aminocarboxyphenyl compounds. Suitably, the aromatic
carbocycles described herein may serve as core structures, and therefore, as
templates for designing libraries of compounds to be screened as
pharmaceutical
agents. Suitably, the aromatic carbocycles are G-protein coupled receptor
ligands,
channel blockers and/or enzyme inhibitors.
The terms "resin-bound synthesis" and "solid phase synthesis" are used
herein interchangeably to mean one or a series of chemical reactions used to
prepare
either a single compound or a library of molecularly diverse compounds,
wherein the
chemical reactions are performed on a compound, suitably, an aromatic
carbocycle)
which is bound to a polymeric resin support through an appropriate linkage)
suitably,
an silane linker.
The terms "resin," "inert resin," polymeric resin" or "polymeric resin
support" are used herein at a11 occurrences to mean a bead or other solid
support
such as beads, pellets, disks, capillaries, hollow fibers, needles, solid
fibers, cellulose
beads, pore-glass beads, silica gels, grafted co-poly beads, poly-acrylamide
beads,
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latex beads, dimethylacrylamide beads optionally cross-linked with N,N'-bis-
acryloyl ethylene diamine) glass particles coated with a hydrophobic polymer)
etc.,
i.e., a material having a rigid or semi-rigid surface. The solid support is
suitably
made of, for example) cross linked polystyrene resin, polyethylene glycol-
polystyrene resin, benzyl ester resins or benzhydrylamine resins and any other
substance which may be used as such and which would be known or obvious to one
of ordinary skill in the art. For purposes herein, it will be obvious to the
skilled
artisan, that when the linker to the resin is silicon-based, the above terms
mean any
aliphatic or aromatic polymer which lacks functionality known to participate
in the
additional synthetic chemistry for generation of the derivatized compounds of
this
invention, and which is stable to conditions for protodesilylation. Preferred
polymer
resins for use herein are the Merrifield resin {available commercially from
Nova
Biochem) and the Wang resin (synthesis described below). The compounds (or
libraries of compounds) made by the instant methods may either remain bound to
the
resin which is used to perform the resin-bound synthesis (hereinafter referred
to as
"resin-bound compounds (or libraries)") or not bound to a resin (hereinafter
referred
to as "soluble compounds (or libraries)").
The terms "silane linker" or "silane linker group" are used herein at all
occurrences to mean the moiety which binds the aromatic carbocycle to the
polymeric resin support, which linker comprises a silicon atom bound to an
alkyl
chain comprising one or more methylene groups, said alkyl chain optionally
having
one or more intervening heteroatoms and/or aryl groups, or combinations
thereof.
Suitable silane linkers for use in this invention comprise a moiety of the
following
formula: -D-CH2-Si-R"R"', wherein R" and R"' are independently, C 1 to C6
alkyl,
and D is a C 1 to C2p alkyl chain optionally having one or more intervening
heteroatoms and/or optionally substituted aryl groups. It will be recognized
that the
alkyl chain may contain both intervening heteroatoms and intervening
optionally
substituted aryl groups. Preferably, R" and R"' are independently, C 1 to C4
alkyl)
more preferably, R" and R"' are both methyl or ethyl, more preferably methyl.
The term "aryl silane compound" is used herein at all occurrences to mean an
intermediate compound comprising an aromatic carbocycle having an aromatic
carbon and at least one substituent X, A) B or C that is not hydrogen or
alkyl,
wherein the aromatic carbon is bound to a silane linker through an aryl silane
bond.
Suitably, an aryl silane compound within the scope of this invention is
defined by a
compound of Formula (IB).
The term "aryl silane bond" is used herein at all occurrences to mean the
bond between the aromatic carbon of an aromatic carbocycle and the silicon
atom of
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a silane linker. Suitably, after the resin-bound synthesis is performed, this
bond is
cleaved in order to decouple the aromatic carbocycle from the resin-bound aryl
silane intermediate.
The term "resin-bound aryl silane intermediate" is used herein at all
occurrences to mean an intermediate wherein an aromatic carbocycle is directly
bound to a silane linker, which linker is directly bound to a polymeric resin
support.
Therefore) it will be recognized that a resin-bound aryl silane intermediate
is a
moiety which couples an aromatic carbocycle to a polymeric resin support
through a
silane linker.
The terms "substituent X," "substituent A," "substituent B," and "substituent
C" are used herein at all occurrences to mean a non-nucleophilic substituent,
including, but not limited to, hydrogen, halogen, alkyl, alkenyl, alkynyl,
alkoxy,
aryloxy, thioether (e.g., -alkyl-S-alkyl-)) alkylthio (e.g., alkyl-SH),
C(O)Ra, wherein
Ra is hydrogen or alkyl) t-butoxyamino-carbonyl, cyano, nitro (-N02), aryl,
heteroaryl, arylalkyl, alkyl disulfide (e.g., alkyl-S-S-)) aryl disulfide
(e.g., aryl-S-S-),
acetal (alkyl(O-alkyl)2), thioacetal (alkyl(S-alkyl)2),
fluorenylmethoxycarbonyl or
orthoester (-C(OR)g, wherein R is C1 to C4 alkyl). The substituents X) A, B
and C
are chosen independently from one another. In addition, X, A, B and C can not
all
be hydrogen and X) A, B and C can not all be alkyl. When the aromatic
carbocycle
is a biphenyl, the substituents X, A, B or C may be, independently, on one or
both
rings. This is similarly so for other aromatic carbocyclic rings or ring
systems as
defined above. As used herein, modification of the substituents produces a
derivatized aromatic carbocycle. The nature of the substituents X, A, B and C,
must
be compatible with the reaction conditions used for modifying said
substituents
without said conditions being capable of cleaving the aryl silane bond of the
resin-
bound aryl silane intermediate. Therefore, it will be recognized that when
modification of substituents X, A, B or C by performing additional synthetic
chemistry thereon, utilizes reaction conditions such that the aryl silane bond
is
subject to cleavage, it is desirable to choose a strong electron withdrawing
group as
the substituent(s). Additional synthetic chemistry can then be performed to
modify
the substituent(s) without cleavage of the aryl silane bond. Subsequent to
performing the additional synthetic chemistry to modify the substituent(s), it
is
possible to cleave the aryl silane bond which decouples the aromatic
carbocycle
from the resin-bound aryl silane intermediate. If desired, synthetic chemistry
conventional in the art may then be performed on the cleaved derivatized
aromatic
carbocycle to convert the strong electron withdrawing group into a different
functionality, e.g., conversion of a nitro group into an amino group using
known
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reaction conditions. Given this disclosure) the types of synthetic chemistry
which
are compatible with the goal of derivatizing the resin-bound aromatic
carbocycle,
without also cleaving the aryl silane bond of the resin-bound aryl silane
intermediate, will be obvious to one of ordinary skill in the art.
The term "additional synthetic chemistry" is used herein at all occurrences to
mean one or a series of chemical reactions which are performed on the resin-
bound
aryl silane intermediate, in particular to modify or derivatize substituents
X, A, B
and C, prior to cleavage of the aromatic carbocycle from the resin-bound aryl
silane
intermediate, wherein said chemical reactions are compatible with and non-
reactive
with the aryl silane bond and may be used to prepare derivatives of the
aromatic
carbocycle. It will be recognized by the skilled artisan that the additional
synthetic
chemistry performed on the resin-bound aryl silane intermediate is done so
prior to
cleavage of the aryl silane bond. Chemical reactions which are compatible with
the
resin-bound aryl silane intermediate, are reactions which effectuate the
swelling of
the polymeric resin thereby allowing penetration of the reagents to react with
the
aromatic carbocycle. Chemical reactions which are reactive with the aryl
silane
bond) i.e., they cause cleavage of the aryl silane bond, and therefore are not
among
the additional synthetic chemistry that may be used in the methods of this
invention,
are for example, chemical reactions which use strongly acidic conditions or
strong
electrophilic oxidizing agents (e.g., benzoyl peroxide under acidic
conditions).
The term "G-protein coupled receptor(s)" is used herein at a11 occurrences to
mean a membrane receptor using G-proteins as part of their signaling
mechanism,
including, but not limited to muscarinic acetykholine receptors, adenosine
receptors,
adrenergic receptors, IL-8R receptors, dopamine receptors, endothelin
receptors,
histamine receptors, calcitonin receptors, angiotensin receptors and the like.
The term "assay" is used herein at a11 occurrences to mean a binding assay or
a functional assay known or obvious to one of ordinary skill in the art,
including, but
not limited to, the assays disclosed herein. A particularly suitable assay for
use
according to the invention is disclosed by Lerner et aL, Proc. Natl. Acad.
Sci. U.S.A.,
91 (5), pp. 1614-16l8 (l994).
The terms "batches" or "pools" are used herein at a11 occurrences to mean a
collection of compounds or compound intermediates.
The term "alkyl" is used herein at all occurrences to mean a straight or
branched chain radical of 1 to 20 carbon atoms, unless the chain length is
limited
thereto, including, but not limited to methyl, ethyl, n-propyl, isopropyl, n-
butyl, sec-
butyl, isobutyl, tent-butyl, and the like. Preferably the alkyl chain is 1 to
10 carbon
atoms in length, more preferably 1 to 8 carbon atoms in length.
_g_
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The term "alkenyl" is used herein at all occurrences to mean a straight or
branched chain radical of 2-20 carbon atoms, unless the chain length is
limited
thereto, including) but not limited to, ethenyl, 1-propenyl, 2-propenyl, 2-
methyl-1-
propenyl, 1-butenyl, 2-butenyl, and the like. Preferably, the alkenyl chain is
2 to 10
carbon atoms in length, more preferably, 2 to 8 carbon atoms in length.
The term "alkynyl" is used herein at all occurrences to mean a straight or
branched chain radical of 2-20 carbon atoms, unless the chain length is
limited
thereto, wherein there is at least one triple bond between two of the carbon
atoms in
the chain, including, but not limited to, acetylene, 1- propylene, 2-
propylene, and the
like. Preferably) the alkynyl chain is 2 to 10 carbon atoms in length, more
preferably, 2 to 8 carbon atoms in length.
In all instances herein where there is an alkenyl or alkynyl moiety as a
substituent group, the unsaturated linkage, i.e., the vinylene or acetylene
linkage is
preferably not directly attached to a nitrogen, oxygen or sulfur moiety.
The term "alkoxy" is used herein at all occurrences to mean a straight or
branched chain radical of 1 to 20 carbon atoms, unless the chain length is
limited
thereto, bonded to an oxygen atom) including, but not limited to, methoxy,
ethoxy,
n- propoxy, isopropoxy, and the like. Preferably the alkoxy chain is 1 to 10
carbon
atoms in length, more preferably 1 to 8 carbon atoms in length.
The terms "cycloalkyl" and "cyclic alkyl" are used herein at all occurrences
to mean cyclic radicals) preferably comprising 3 to 10 carbon atoms which may
be
mono- or bicyclo- fused ring systems which may additionally include
unsaturation,
including, but not limited to, cyclopropyl, cyclopentyl, cyclohexyl, 1,2,3,4-
tetrahydronaphthyl, and the like.
The terms "aryl" or "heteroaryl" are used herein at all occurrences to mean 5-
14 membered optionally substituted aromatic rings) or ring systems which may
include bi- or tri-cyclic systems and one or more heteroatoms, wherein the
heteroatoms are selected from oxygen, nitrogen or sulfur. Representative
examples
include, but are not limited to, phenyl, naphthyl, pyridyl, quinolinyl,
thiazinyl,
isoquinoline, imidazole, 3,4-dimethoxyphenyl) 3,4-methylenedioxyphenyl, 3,4-
dimethoxybenzyl, 3,4-methylenedioxy-benzyl, benzhydryl, 1-naphthylmethyl, 2-
naphthylmethyl) fluorenyl, biphenyl-4-methyl, furanyl, and the like.
The term "heteroatom" is used herein at all occurrences to mean an oxygen
atom ("O"), a sulfur atom ("S") or a nitrogen atom ("N"). It will be
recognized that
when the heteroatom is nitrogen, it may form an NR 1 R2 moiety, wherein R 1
and R2
are) independently from one another, hydrogen or C 1 to Cg alkyl, or together
with
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the nitrogen to which they are bound, form a saturated or unsaturated S-, 6-,
or 7-
membered ring.
The terms "aryialkyl" and "heteroarylalkyl" are used herein at all occurrences
to mean an aryl or heteroaryl moiety, respectively, that is connected to a C 1
_g alkyl
moiety as defined above, such as, but not limited to, benzyl.
The term "5- 6-) or 7-membered ring" is used herein at a11 occurrences to
mean that substituents R1 and R2, together with the nitrogen to which they are
bound, form a saturated or unsaturated ring structure containing at least one
additional heteroatom selected from oxygen, nitrogen or sulfur, including, but
not
limited to morpholine, piperazine, piperidine, pyrolidine, pyridine, and the
like.
The term "heterocyclic" is used herein at all occurrences to mean a saturated
or wholly or partially unsaturated 4-10 membered ring system in which one or
more
rings contain one or more heteroatoms selected from the group consisting of O,
N, or
S; including, but not limited to, pyrrolidine, piperidine, piperazine,
morpholine,
imidazolidine, pyrazolidine, benzodiazepines, and the like.
The term "halogen" is used herein at all occurrences to mean chloro, fluoro,
iodo and bromo.
The term "Ph" is used herein at all occurrences to mean phenyl.
The term "optionally substituted" is used herein at all occurrences to mean
that
the optionally substituted moieties may or may not be substituted with one to
three
various functional groups including, alkyl, alkenyl, alkynyl, aryl,
cycloalkyl,
heteroaryl, heterocyclo groups arylalkyl, heteroarylalkyl, halogen, cyano, -
(CR 11 R 12)n_C(O)R~; _(CR 11 R 12)n_N02; -(CR 11 R 12)n-OR' ~ (CR 11 R
12}n_SR'; -
(CR11R12)n_N(R')2; -(CR11R12)n_NHC(O)R'; -(CR11R12)n_C02R';-(CR11R12)n_
CON(R')2; -(CR11R12)a(C=C)b(CR11R12)cZ' or
(CR 11 R 12)a(C=C)bW'(CR 11 R 12)cZ'; wherein Z' is C(O)R', C02R', N02; OR';
SR';
N(R'}2 , NHC(O)R'; or CON(R')2; a is 0 or l, b is 0 to 10 and c is 0 to 10)
preferably
a=b=c is less than 10; W' is N or S; R' is hydrogen, (C1 - C4) alkyl, aryl,
arylalkyl, or
heteroaryl; and R 11 and R 12 are independently hydrogen or a branched or
straight
chain C 1 to C6 alkyl, alkenyl or alkynyl; and, for purposes herein, n is 0 or
is an
integer from 1 to 10. It is recognized that these substituents may be further
substituted
by groups similar to those indicated above herein to give substituents such as
halo-
substituted alkyl (e.g., -CF3), aryl-substituted alkyl, alkoxy-substituted
alkyl and the
like. For example, in the term (CR 11 R 12)n-N(R')2, n is 1, R 11 is -
CH2CH=CH2, R 12
is hydogen, one of R' is hydrogen and one of R'is benzyl; in the term -
(CR11R12)nSR',
n is 1, R' is phenyl, R 12 is hydrogen, R 11 is a substituted alkyl,
specifically a methyl
substituted by -COOR' and R' is hydrogen, methyl or ethyl; in the term
alkenyl, the
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WO 98117695 PCTIUS97119450
alkenyl moiety may be substituted by -(CR 11 R 12)n_C(O)R' or -(CR 11 R 12)n-
C02R',
wherein R' is hydrogen) methyl or ethyl; in the term (CR 11 R 12)a(C=C)b(CR 11
R 12}c
Z',ais l,bis l,cisO,Z'isNR',R11 andRl2areHandR'isbenzyl;intheterm
(CR 11 R 12)a(C=C)bW'(CR 11 R 12)cZ') W' is N and a is 1) b is 1, c is 0) Z'
is NR', R 11
and R12 are H and R' is benzyl.
Preferred optional substituents for use herein include alkyl, alkenyl, alkoxy,
cyano, N02, halogen) preferably bromine, -(CR 11 R 12)nC(O)R') -(CR 11 R
12)n_S R')
-(CR 11 R 12)n_N(R'}2 and aryl, preferably phenyl. More preferably) the
optional
substituents are C ~ to C lp alkyl, C 1 to C ~ p alkoxy, cyano, C(O)R', N02,
halogen,
and aryl.
The term "polypeptide" is used herein at all occurrences to mean a polymer
of amino acids (i.e.) acid units chemically bound together with amide linkages
(CONH)), forming a chain that consists of 1 to 20 amino acid residues.
Certain non-peptide compounds bind to a variety of receptors, particularly,
G-protein coupled receptors. Suitably, the following core structures may be
used as
templates for designing libraries of non-peptide compounds which may be tested
for
binding to a variety of receptors, specifically) G-protein coupled receptors.
25
Benzodiazepines of formula (I):
H O
N
1
N
2 '
Formula (I}
N-phenylimidazoles of formula (II):
1
CO BFI
N
~2
Formula (II)
Oxindoles of formula (III):
11-
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WO 98I17695 PCT/US97119450
N O
Formula (III)
Indole carboxylic amines or acids of formula (IV):
Formula (IV)
Aminobenzazepines of formula (V):
O
NH
W i
N
O
Formula (V)
Surprisingly, it has been discovered that compounds which comprise any one
of these core structures, when tested in assays developed for determining lead
compounds as pharmaceutical agents, demonstrate activity more often than would
be
expected by the skilled artisan. These core structures may be used as
templates for
developing synthetic libraries by the combinatorial methods described herein.
The
libraries of compounds can then be screened in assays developed for
determining
lead compounds as pharmaceutical agents. If the core structures are used as
templates for making the libraries of compounds, the number of individual
compounds which are likely to be active in a particular assay will be higher
than the
skilled artisan would expect when using standard methods of synthesizing
individual
compounds randomly for screening as pharmaceutical agents. Also, by making and
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screening the libraries of compounds based upon core structures, the
probability of
identifying a chemical lead for use as a pharmaceutical agent is enhanced.
Combinatorial Svnthesis Methods:
S Based upon the disclosure herein, it will be clear to one of ordinary skill
in
the art that there are many possible synthetic approaches to creating the
libraries of
this invention. The libraries can be prepared on a solid support, e.g., a
resin, or they
can be prepared in solution. For example, the variable substituents can be
added by
reacting core structure, labeled R, with a mixture of reagents designed to
introduce
substituents X 1 _m collectively or by reacting aliquots of R with individual
reagents
each one of which will introduce a single substituent Ri and then mixing the
resultant products together (wherein i, j and k are used herein to represent
any of the
substituents on the compound members of the combinatorial library).
For reasons of efficiency) the components of the library are screened in
groups of multiple compounds. Therefore, once the library of compounds has
been
synthesized) there must be some method to deconvolute the results of screening
such
that individual active compounds can be identified. Based upon the disclosure
herein, it will be clear to the skilled artisan that there are many methods
for
deconvolution of the combinatorial library. For example) if the compounds of
the
library are screened on a solid support) they may be physically segregated so
that
individual active compounds may be directly selected and identified. In
contrast, if
the compounds of the library are tested as soluble mixtures, the library may
be
deconvoluted in an iterative approach, which involves resynthesis of mixtures
of
decreasing complexity until a single compound is identified, or in a scanning
approach, in which the various substituents on the core structure R) are
evaluated
independently and the structure of active compounds are determined
deductively.
Both the iterative and scanning approaches to deconvolution of the
combinatorial
libraries of this invention are described in more detail below.
Iterative aunroach
In its simplest form, the iterative approach to deconvoluting the
combinatorial library involves separation of the combinatorial library of
compounds
immediately prior to the introduction of the last variable substituent. Using
the same
nomenclature, i.e., R is the core structure, etc., as used above, the mixture
of
compounds RX 1 _rnY 1 _n is partitioned into p aliquots (wherein m, n and p
are
integers which define the size of the library, and which range between 1 to
1000;
preferably between 1 to 100; most preferably between 1 to 20). Each of those
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aliquots is reacted with reagents designed to introduce a single substituent,
labeled
Z. Thus, p different pools RX1_mYl-nZi, each of which contains m x n compounds
with all possible variations of X and Y being represented but only one
particular Z,
will be obtained. Screening this library in a binding or functional assay
defines the
appropriate Z substituent(s) for the desired activity.
Once the appropriate Z substituent, labeled Za, is determined (for
illustrative
purposes, only one active compound exists, however, it would be clear to the
skilled
artisan that more than one active compound may exist in the library), the
library is
prepared again, this time splitting the mixture of compounds RX 1 _m into n
aliquots
for introduction of the n different Y substituents (as used herein "a", "b"
and "c"
refer to specific acceptable substituents which have been determined to be
active by
screening in a binding or functional assay). After the Y substituents are
introduced,
the Za substituent is introduced into each of the still separated aliquots.
The library
now consists of n pools RX 1 _mYjZa, each of which contains m different
compounds
with all the possible X substituents represented, and one particular Y
substituent.
Screening this library in a binding or functional assay defines the
appropriate Y
substituent, labeled Yb.
In a similar manner, the appropriate X substituent) labeled X~ is determined
by beginning with m different aliquots of core structure R and sequentially
introducing Xk, Yb and Za to give m different pools RXkYgZa, each of which
contains a single compound. Thus only m + n + p syntheses are required to
deconvolute a library containing m x n x p compounds.
The iterative approach is specific for a single target which is determined
after
the first round of screening, since subsequent library preparations do not
contain the
full complement of substituents.
Scanning approach
The application of the scanning approach to deconvoluting the combinatorial
library requires that the variable substituents X, Y and Z can be introduced
synthetically independently of each other. The library is first prepared as
~ 1-mY 1-nZi exactly as in the iterative approach to give p pools RX 1 _mY 1
_nZi,
each of which contains m x n compounds with all possible variation of X and Y
represented but only one particular Z. Screening this library defines the
appropriate
Z substituents for the desired activity.
Since Y can be introduced independently from X and Z, the library is then
prepared as RX 1 _mYjZ 1 _ p, giving n pools of compounds each containing m x
p
compounds in which all substituents X and Z are represented with a particular
Y
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substituent. Screening this library in a binding or functional assay defines
the
appropriate Y substituents for the desired activity.
Since X can also be introduced independently from Y and Z, the library is
then prepared as RXkY 1-nZ1-p) giving m batches or pools of compounds, each of
which contains n x p compounds in which all substituents Y and Z are
represented
with a particular X substituent. Screening this library in a binding or
functional
assay defines the appropriate X substituents for the desired activity.
In the simplest case, a single X, Y and Z substituent are identified from the
three libraries, thus converging on a single compound RX~YgZa. The advantage
of
utilizing the scanning approach is that each library contains all the possible
permutations of X, Y and Z and can be utilized to screen against a number of
different biological targets.
The Use of Silicon Chemistry in Preparing Combinatorial Libraries
The use of the instant silicon-based resins has been discovered to be
particularly effective in preparing, by resin-bound synthesis, core
structures) which
are substituted aromatic carbocycle(s), wherein said aromatic carbocycle(s)
comprises an aromatic carbon which carbon has a hydrogen, halogen, hydroxy or
acyloxy group bound to it after the resin-bound synthesis is completed. The
aromatic carbocycle prepared by resin-bound synthesis utilizing silicon
chemistry
may be useful as receptor ligands, particularly G-protein coupled receptor
ligands,
enzyme inhibitors and channel blockers.
In contrast to the resins and linkers known in the art, the instant polymeric
resins and silane linkers are particularly useful in effectuating the cleavage
of an
aromatic carbocycle from a polymeric resin support while leaving a hydrogen at
the
cleavage position. In addition, the silicon linkers, polymeric resin supports
and
intermediates of this invention effectuate the successful preparation of a
single
aromatic carbocycle or a plurality of molecularly diverse aromatic carbocycles
which, upon cleavage from a polymeric resin support, have a halogen, hydroxy
or
acyloxy group at the cleavage position. The aromatic carbocycles prepared by
the
methods described herein can be screened in assays developed far determining
lead
compounds as pharmaceutical agents.
In one aspect, the invention is in a method for preparing a compound by
resin-bound synthesis, wherein said compound is an aromatic carbocycle
comprising
an aromatic carbon atom and at least one substituent that is not hydrogen or
alkyl,
said method comprising the steps of: (i) attaching the aromatic carbon to a
polymeric resin support through a silane linker to give a resin-bound aryl
silane
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Intermediate; and (ii) performing additional synthetic chemistry on the
substituent
so that the aromatic carbocycle is derivatized. The derivatlzed resin-bound
aryl
silane intermediate may be stored for further derivatization of the
substituents.
Suitably, the aromatic carbocycle is biphenyl, phenyl, naphthyl or
anthracenyl.
Suitably, the aromatic carbocycle has at least one substituent that is X) A, B
or C, as
defined above, to be derivatized by additional synthetic chemistry. A compound
prepared by this method remains as a resin-bound aryl silane intermediate)
which
resin-bound intermediate may be screened in a suitable assay developed for
determining pharmaceutical activity.
The derivatized aromatic carbocycle may be decoupled from the resin-bound
aryl silane intermediate by a further step comprising cleaving the resin-bound
aryl
silane intermediate at the aryl silane bond so that the decoupled aromatic
carbocycle
resulting from the cleavage has a hydrogen, halogen, hydroxy or acyloxy group
on
the aromatic carbon where it was bound through the silane linker. After this
step,
the decoupled aromatic carbocycle may be screened in a suitable assay
developed for
determining pharmaceutical activity.
As described above, the additional synthetic chemistry performed in order to
modify the substituents X, A, B or C must be such that the aromatic carbocycle
is
derivatized without cleaving the aryl silane bond of the resin-bound aryl
silane
intermediate.
According to this invention, the aromatic carbocycle is bound to a polymeric
resin support through a silane linker to give a resin-bound aryl silane
intermediate. In
particular, the aromatic carbocycle is bound to the resin through a silane
linker group
comprising the following moiety: D-CH2-Si-R"R"', wherein D is defined as a C 1
to C2o
alkyl chain optionally having one or more intervening heteroatoms andlor
optionally
substituted aryl groups, and R" and R"' are independently, C 1 to C6 alkyl.
Preferred
silane linker groups of formula D-CH2-Si-R"R"' for use in the methods
disclosed herein
include, but are not limited to, the following linker groups: -(CH2)4-Si-
R"R"', wherein
D is -(CH2)3-; -O-CH2-Ph-O-CH2-Si-R"R"', wherein D is -O-CH2-Ph-O-; -O-Ph-O-
CH2-SiR"R"', wherein D is -O-Ph-O-; or -O-Ph-CH2-O-CH2-Si-R"R"', wherein D is -
O-Ph-CH2-O-. A preferred silane linker group for preparing aromatic
carbocycles
wherein a substituent X, A, B, or C is cyano, is a~linker group of formula D-
CH2-Si-
R"R"', wherein D is -O-Ph-O-. For purposes herein, the aromatic carbon atom of
the
aromatic carbocycle is bound directly to a silicon atom of the silane linker.
Preferably,
R" and R"' are independently, C 1 to C4 alkyl) more preferably, R" and R"' are
both
methyl or ethyl, more preferably R" and R"' are both methyl.
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Useful intermediates of the invention are the novel aryl silane compounds of
Formula (IB). The compounds of Formula (IB) are reacted with an appropriate
polymer resin in order to make a resin-bound aryl silane intermediate which
will be
further modified by performing additional synthetic chemistry thereon.
Preferably,
an aryl silane compound is formed as a first intermediate, which intermediate
is then
coupled to a polymeric resin support. A suitable resin-bound aryl silane
intermediate is prepared by combining an aryl silane compound of Formula (IB):
R"
A
O ~ Si
OH ( / n R... I x X
C
Formula (1B)
wherein R" and R"') independently from one another, are C1 to C6 alkyl; X, A,
B and
C are, independently from one another, hydrogen, halogen, alkyl, alkenyl,
alkynyl,
alkoxy, alkylthio, C(O)Ra, wherein Ra is hydrogen or alkyl, t-
butoxyaminocarbonyl,
cyano, nitro, aryl, heteroaryl, arylalkyl) alkyl disulfide, aryl disulfide,
acetal,
fluorenylmethoxycarbonyl or orthoester group, provided that X, A, B and C can
not
all be hydrogen and X, A) B and C can not all be alkyl; and n is an integer
from 1 to
10) with an appropriate polymeric resin) using conventional techniques.
A preferred embodiment of this inventive intermediate is a compound of
Formula (IB) wherein R" and R"', independently from one another, are Cl to C~
alkyl; X is bromine or iodine; A, B and C are hydrogen; and n is 1 to 4. A
more
preferred embodiment of this invention is wherein R" and R"' are each methyl;
X is
bromine; A, B and C are hydrogen; and n is 1.
The compound of Formula (IB) may then be reacted with a suitable
polymeric resin support to form a resin-bound aryl silane intermediate.
Suitable
resins for use herein are a cross-linked polystyrene resin; a polyethylene
giycol-
polystyrene based resin, or a polypropylene glycol based resin. A preferred
resin for
reaction with a compound of Formula (IB) is a chloromethyl cross-linked
divinylbenzene polystyrene resin. Suitable additional synthetic chemistry may
be
performed on this resin-bound aryl silane intermediate, particularly on the
substituents X, A, B or C, as described above) in order to modify the
substituents X,
A, B or C.
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In all cases, after the aromatic carbocycle portion of the resin-bound aryl
silane intermediate is modified by the additional synthetic chemistry, the
derivatized
aromatic carbocycle may be cleaved from the resin-bound aryl silane
intermediate at
the aryl silane bond or it may remain as a resin-bound aryl silane
intermediate.
The intermediate compounds of Formula (IB) may be prepared by utilizing
another useful intermediate of this invention, i.e., a compound of Formula
(IIB}:
x
A W
B
S1(R"R"'XCHZ) ~ -Y
Formula (IIB)
wherein R" and R"', independently from one another, are C 1 to C6 alkyl; X, A,
B and
C are, independently from one another, hydrogen, halogen) alkyl, alkenyl,
alkynyl,
alkoxy, alkylthio, C(O)Ra, wherein Ra is hydrogen or alkyl, t-
butoxyaminocarbonyl,
cyano, nitro) aryl, heteroaryl, arylalkyl, alkyl disulfide, aryl disulfide)
acetal,
fluorenyImethoxycarbonyl or an orthoester group, provided that X, A, B and C
can
not a11 be hydrogen and X, A, B and C can not all be alkyl; Y is halogen or
hydroxyl; and n is an integer from 1 to 10. A preferred embodiment of this
aspect of
the invention is a compound of Formula (IIB) wherein R" and R"', independently
from one another, are Cl to C4 alkyl; X is halogen; A, B and C are hydrogen; Y
is
bromine; and n is 1 to 4. A more preferred embodiment of this aspect of the
invention is a compound of Formula (IIB) wherein R" and R"' are each methyl; X
is
bromine; A, B and C are hydrogen; Y is bromine; and n is 1. As would be
obvious
to one of ordinary skill in the art, the novel intermediates of Formula (IIB)
may
easily be prepared from compound 1-Scheme 1) or appropriate analogs thereof,
by
reaction with an alkyl lithium compound. In the alternative, a compound of
Formula
(IIB) may be prepared by forming a Grignard reagent of compound 1-Scheme 1, or
appropriate analogs thereof. An illustrative method for preparing an
intermediate of
Formula (IIB) is disclosed by Morikawa et al., Polym. J.) 24, p. 573 (1992),
the
relevant parts of which are incorporated herein by reference. In addition, as
would
be appreciated by the skilled artisan, aside from being compatible with the
additional
synthetic chemistry to be performed on the resin-bound aryl silane
intermediate,
substituents X, A, B and C must also be compatible with the alkyl lithium
chemistry
utilized to make the intermediates of Formulae (IB) and (IIB).
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In order to cleave the aryl silane bond of the resin-bound aryl silane
intermediate, so that a hydrogen is bound to the aromatic carbon at the
cleavage site,
a number of suitable conditions may be used, for example, treatment of the
resin-
bound aryl silane intermediate with a strong protic acid. In particular, the
acidic
cleavage conditions, include, but are not limited to) treatment with 100%
trifluoroacetic acid ("TFA"), hydrofluoric acid ("HF"), hydrochloric acid
("HCl"),
pyridinium hydrofluoride, sulfuric acid ("H2S04")) trifluoromethanesulfonie
acid
(commonly referred to as triflic acid}, boron trifluoride ("BFg"),
methanesulfonic
acid or mixtures thereof. Preferred cleavage conditions utilize 100% TFA.
Alternatively, cleavage of the aryl silane bond may be accomplished using base
catalyzed cleavage. In particular) base catalyzed cleavage conditions include,
but are
not limited to, cleavage with NaOH in DMSO (dimethylsulfoxide) or methanol.
See, for example, Cretney et al.) J. Organometal. Chem., 28, pp. 49-52 ( 1971
).
In order to cleave the aryl silane bond of the resin-bound aryl silane
intermediate so that a halogen is bound to the aromatic carbon at the cleavage
site, a
number of suitable conditions may be used, for example, treatment of the resin
bound aryl silane intermediate with bromine, chlorine or iodine.
In order to cleave the aryl silane bond so that a hydroxy group is bound to
the
aromatic carbon at the cleavage site, a number of suitable conditions may be
used,
for example, treatment of the resin-bound aryl silane intermediate with
benzoyl
peroxide to give a benzoate ester at the cleavage site. The resulting aromatic
carbocycle which is substituted with an ester functionality may be
subsequently
hydrolyzed using known conditions to yield an aromatic carbocycle which is
substituted with a hydroxy group.
In order to cleave the aryl silane bond so that an acyloxy group is bound to
the aromatic carbon at the cleavage site, a number of suitable conditions may
be
used, for example) treatment of the resin-bound aryl silane intermediate with
acetyl
peroxide or any suitable acyl peroxide using conventional conditions known to
the
skilled artisan.
In yet another aspect, this invention is in a method for preparing a library
of
diverse resin-bound aromatic carbocycles each comprising an aromatic carbon
atom
and at least one substituent that is not hydrogen or alkyl, said method
comprising the
steps of: (i) attaching the aromatic carbon atom of each of a plurality of
aromatic
carbocycles to an individual polymeric resin support through a silane linker
to give a
plurality of resin-bound aryl silane intermediates; (ii) optionally dividing
said
resin-bound aryl silane intermediates into a plurality of portions; {iii)
performing
additional synthetic chemistry on the substituents so that the aromatic
carbocycle is
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derivatized; and (iv) optionally recombining the portions. Suitably) the
substituents
on the aromatic carbocycle which are to be derivatized are X, A, B or C as
defined
above.
Based upon the disclosure herein, it will be clear to one of ordinary skill in
the art that there are many possible synthetic approaches to preparing the
libraries of
this invention. The libraries are considered to be combinatorial libraries
because the
compounds generated from the synthetic methods are molecularly diverse and are
prepared simultaneously. The libraries may be prepared on polymeric resin
supports
using the silane linkers described herein above.
For example, a plurality of aromatic carbocycles each comprising an
aromatic carbon atom and having at least one substituent X) A, B or C that is
not
hydrogen or alkyl, are each attached to an individual polymer resin support
through
a silane linker to give a plurality of resin-bound aryl silane intermediates.
In a first
step modification to the substituent(s) on the aromatic carbocycle, the
plurality of
resin-bound aryl silane intermediates may be reacted with one or more reagents
in
one reaction vessel. Alternatively in a first step modification, aliquots of
the resin-
bound aryl silane intermediates may be reacted with one or more reagents and
then
the resultant products are mixed together to form a library of derivatized
aromatic
carbocycles. Preferably, the reagents) used in this first step modification
will
modify only a single substituent X, A, B or C.
This first modifiedlderivatized library may then be further derivatized by
repeating the process of dividing and recombining the derivatized resin-bound
aryl
silane intermediates formed by the additional synthetic chemistry. It will be
obvious
to the skilled artisan that the resin-bound aryl silane intermediates may be
divided
into portions at any point during the synthetic scheme. The portions may be
recombined at any point during the scheme or, further iterations may be
applied if
more derivatization is required. For example, after a first step modification
where
the aliquots were divided and reacted with one or more appropriate reagents,
the
derivatized aliquots may be recombined and reacted with one or more additional
reagents in one reaction vessel. Alternatively, each aliquot may be subdivided
into
further aliquots and reacted as described herein.
Therefore, it will be obvious to the skilled artisan that the steps of
dividing
the portions, performing additional synthetic chemistry and recombining the
portions, may each be carried out more than once. The steps of optionally
dividing
and recombining the resin-bound aryl silane intermediates into portions are
for
purposes of varying the derivatization, depending upon the type of diversity
required
for the library of end-product aromatic carbocycles being prepared by the
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WO 98I17695 PCT/US97119450
combinatorial synthesis. Suitably, when the libraries of the invention are
prepared
according to the instant disclosure, each polymeric resin support bears a
single
(derivatized) aromatic carbocycle species created by the additional synthetic
chemistry performed on the resin-bound aryl silane intermediate.
For example, in Scheme 6, if the desired library is one that comprises an N-
methylated compound of formula 8 and an N-ethylated compound of formula 8, the
following variation on the split-synthesis method of Moss et al., Ann. Rep.
Med.
Chem., 28, p. 315 ( 1993), for preparing libraries of compounds may be used.
The
steps depicted in Scheme 6 are followed) without dividing the resin-bound aryl
silane intermediates of formulae 1 through 5 into portions. However, prior to
N-
alkylation of the resin-bound aryl silane intermediate of formula 6) said
resin-bound
formula 6 is divided into a number of portions, for example, two portions,
labeled
for purposes of illustration as portion 1 and portion 2. Each of the two
portions
contains resin-bound aryl silane intermediate 6-Scheme b. Portion 1 is reacted
under
standard conditions with) e.g.) methyl iodide, in order to obtain a compound Z
Sc m , wherein R4 is methyl. Portion 2 is reacted under standard conditions,
with, e.g., ethyl bromide) in order to obtain compound 7-Scheme 6, wherein R4
is
ethyl. The two separate portions are recombined to form a library of two
compounds) wherein each polymer resin is linked through a silane linker group,
to a
distinct aromatic carbocycle which is the product of a specific reaction
sequence.
The methods and linkers described herein may be applied to the preparation
of a large variety of core structures, including aromatic carbocycles.
However) when
utilizing the silicon-based linkers and resin-bound aryl silane intermediates
disclosed
herein, the silicon linker group (which comprises D-CH2-Si-R"R"') is suitably
bound
2S to an aromatic carbon on the aromatic portion of the core structure, such
as in a
benzodiazepine derivative or in a tetrahydronaphthyl derivative.
According to this invention, after the additional synthetic chemistry has been
performed on the resin-bound aryl silane intermediate so that a library of
molecularly diverse compounds has been prepared, the compounds can be
separated
and characterized by conventional analytical techniques known to the skilled
artisan,
for example infrared spectrometry or mass spectrometry. The compounds may be
characterized while remaining resin-bound or they can be cleaved from the
resin-
bound aryl silane intermediates using the conditions described above, and then
analyzed.
In addition) some of the compound members of the library may be cleaved
from the resin-bound aryl silane intermediates while other members of the
library
remain resin bound to give a "partially cleaved" library of compounds.
Alternatively
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if all of the members of the library of compounds are cleaved from the resin-
bound
aryl silane intermediates, a "fully cleaved" library of compounds is created.
General Methods of Preparation
For all of the following Schemes, standard work-up and purification methods
can be used and will be obvious to the skilled artisan. In addition, it will
be
recognized that the aromatic carbocycles coupled to the polymerc resins
through the
silane linkers illustrated below, can be optionally substituted at any
appropriate site,
depending upon the type of derivatization required. In particular, when the
aromatic
carbocycle is a biphenyl, the substituents X, A, B or C may be, independently,
on
one or both rings. This is similarly so for other aromatic carbocyclic rings
or ring
systems) as defined above.
As used herein) the following terms have the foliowing meanings: "DMF" is
dimethylformamide; "DMSO" is dimethylsulfoxide; "LRMS" is low resolution mass
spectrometry; "DIEA" is diisopropylethylamine; "THF" is tetrahydrofuran; "n-
BuLi"
is n-butyliithium; "min" is minutes; "h" or "hr" is hours; "mL" is
milliliters; "RT" or
"rt" is room temperature; "BnBr" is benzylbromide; and"OAc" is acetate.
Scheme 1
The resin-bound aryl silane intermediate 4-Scheme 1, wherein X is bromine
and A, B and C are each hydrogen, is prepared by reacting Merrifield
chloromethyl
resin (available from Nova Biochem, 1.4 mMlg of Cl) with the resin-bound aryl
silane intermediate alcohol 3-Scheme 1, wherein X is bromine and A, B and C
are
each hydrogen, in an SN2 displacement as described in Scheme i .
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WO 98I17695 PCT/U597/19450
.. X
\ a \
/ I/
Br Si(Me)2 CHz Br
1
I \ O\/ ~ ( \ c
HO
X
/I i\ ~''~~ (\
\ O / /
X
(a) n-BuLi, THF, -7$~C, BrCH2Si(Me)2Cl [bromomethyl chlorodimethyl silane,
available from Aldrich]; (b) NaOMe, DMF) p-hydroxybenzyl alcohol; (c) NaH,
THF, 70~C, Merrifield resin.
Compounds analogous to intermediate compound 2-Scheme 1 (i.e., a
compound of Formula (IIB) wherein R" and R"' are methyl; X is bromine; A, B
and
C are hydrogen; Y is bromine; and n is 1 ) may be prepared from an optionally
substituted aromatic carbocycle such as 1-Scheme 1 having a substituent(s)
which
can be converted by conventional techniques, such as formation of an alkyl (C1-
Cg)
lithium species, into a haloalkyl dialkylsilyl substituent. 2-Scheme 1 (or the
appropriate analogs) is reacted with a base) {such as sodium methoxide or
potassium
carbonate) in an aprotic solvent (dimethyl formamide, dimethyl acetamide or
DMSO
if sodium methoxide is the base; acetone or ethyl methyl ketone if potassium
carbonate is the base) to displace the halogen on the silane moiety for
coupling with
optionally substituted hydroxybenzyl alcohol to prepare an aryl silane
compound 3-
Scheme 1 (i.e., a compound of Formula (IB) wherein R" and R"' are methyl; X is
bromine; A) B and C are hydrogen; and n is 1 ). An SN2 displacement of 3-Sc a
1_ with a polymer resin is accomplished using strong basic conditions (such as
NaH)
in an aprotic solvent (such as THF, DMSO, DMF or dimethyl acetamide) providing
4-Scheme 1. As will be clear to the skilled artisan) this reaction sequence
can be
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WO 98I17695 PCTIUS97119450
performed on compound 1-Scheme 1, wherein X, A, B and C are, independently
from one another, hydrogen, halogen, alkyl, alkenyl, alkynyl, alkoxy, aryloxy)
thioether, alkylthio, C(O)Ra, wherein Ra is hydrogen or alkyl, t-butoxyamino-
carbonyl, cyano, nitro (-N02), aryl, heteroaryl, arylalkyl, alkyl disulfide,
aryl
disulfide, acetal, fluorenylmethoxycarbonyl or orthoester (-C(OR)g, wherein R
is C 1
to C4 alkyl), provided that X, A, B and C can not all be hydrogen and X, A, B
and C
can not all be alkyl.
Scheme 2
The synthesis of an isomeric resin-bound aryl silane intermediate of 2-
Scheme 2, wherein X is bromine and A, B and C are hydrogen, is depicted
starting
from the Wang resin I-Scheme 2. In addition) Scheme 2 depicts the preparation
of
an aromatic carbocycle (4-Scheme 2, wherein X is bromine) from a resin-bound
aryl
silane intermediate (2-Scheme 2) wherein X is bronune), wherein the aromatic
carbocycle has a hydrogen atom at the site of cleavage from the resin.
/ ~ ~OH
O ~ a
/
P
L / X
b
---s
P
CHO X
/ + ~ /
HO H
(a) 2-Scheme 1, NaH, THF, n-Bu4NI-, 70~C, 4 days; (b) TFA, Neat
The Wang resin 1-Scheme 2 is prepared according to the published
procedure of Su-Sun Wang, JACS, 95, p. 1328 ( 1973) starting from the
Mernfleld
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WO 98I17695 PCT/US97/19450
resin. Elemental analysis of 2-Scheme 2, wherein X is bromine and A, B and C
are
hydrogen, indicated a conversion of approximately 70%. Preparation of a
substituted aromatic carbocycle wherein a hydrogen is left at the site of
cleavage
from the resin is accomplished according to Scheme 2 by treating the resin-
bound
aryl silane intermediate 2-Scheme 2 with strong acidic conditions (such as
TFA,
HCI, H2S04, trifluoromethanesulfonic acid BF3, methanesulfonic acid or
mixtures
thereof] to give a substituted aromatic carbocycle 4-Scheme 2. Again) as will
be
clear to one of ordinary skill in the art, this reaction sequence can be
performed on
compound 2-Scheme 2, wherein X, A, B and C are, independently from one
another,
hydrogen, halogen, alkyl, alkenyl, alkynyl, alkoxy, aryloxy, thioether,
alkylthio,
C(O)Ra, wherein Ra is hydrogen or alkyl, t-butoxyamino-carbonyl, cyano, vitro
(-
N02), aryl, heteroaryl, arylalkyl, alkyl disulfide) aryl disulfide, acetal,
fluorenylmethoxycarbonyl or orthoester (-C(OR)3, wherein R is C i to C4
alkyl),
provided that X, A, B and C can not a11 be hydrogen and X, A, B and C can not
all
be alkyl.
Scheme 3 and Scheme 4
The various chemical reactions outlined in Scheme 3 and Scheme 4 show the
use of the silicon based polymer resins of this invention for the synthesis of
a variety
of substituted aromatic carbocycies. As will be obvious) conventional
chemistry
known to the skilled artisan may be applied to the resin-bound aryl silane
intermediates disclosed herein in order to modify the substituents on the
starting
aromatic carbocycle.
x
~I I~ ~~~ (~ a i
0
x
1 H
X 2
b
Br
(a) TFA) Neat; (b) Br2, CHZC12.
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Reaction sequence (a) depicts the preparation of an aromatic carbocycle 2-
Sc a a , wherein X is, hydrogen) halogen, alkyl, alkenyl, alkynyl, alkoxy,
aryloxy,
thioether, alkylthio, C(O)Ra, wherein Ra is hydrogen or alkyl, t-
butoxyaminocarbonyl, cyano, nitro (-N02), aryl, heteroaryl, arylalkyl, alkyl
disulfide, aryl disulfide, acetal, fluorenylmethoxycarbonyl or orthoester {-
C(OR)3)
wherein R is C 1 to C4 alkyl), preferably halogen, and most preferably
bromine, and
wherein A, B and C are hydrogen. 2-Scheme 3, wherein there is a hydrogen atom
left on the aromatic carbocycle at the cleavage site, is synthesized through
an aryl
silane intermediate which is bound to a suitable resin (such as the Merrifield
resin or
the Wang resin), wherein cleavage of 2-Scheme 3 from the resin is accomplished
using strong acidic conditions. Preparation of an aromatic carbocycle 3-Scheme
3,
wherein there is a halogen atom left on the aromatic carbocycle at the site of
cleavage from the silane resin intermediate is accomplished by reacting the
resin-
bound aryl silane intermediate with an elemental halogen compound (such as
Br2, I2
or CI2) in a suitable aprotic solvent (such as methylene chloride). It will be
obvious
to one of ordinary skill in the art that these reaction sequences may be
applied,
wherein X, A) B and C are, independently from one another, hydrogen, halogen,
alkyl, alkenyl, alkynyl, alkoxy, aryloxy, thioether, alkylthio, C(O)Ra,
wherein Ra is
hydrogen or alkyl, t-butoxyaminocarbonyl) cyano, nitro (-N02), aryl,
heteroaryl,
arylalkyl, alkyl disulfide, aryl disulfide, acetal, fluorenylmethoxycarbonyl
or
orthoester (-C(OR)3, wherein R is C 1 to C4 alkyl), provided that X, A, B and
C can
not a11 be hydrogen and X, A, B and C can not all be alkyl.
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Scheme 4
/I I\ ~~~f I\
\ O / / Br
1
a; b; c
O~ I ( \
\ O ~ ~ X O COZ H
2 a. 2b. 2c X (2a) _
X (2b) = COZ H
X (2c) = COCOZ Et
(a) n-BuLi, THF, Phthalic anhydride (available from Aidrich); (b) n-BuLi, THF,
C02; (c) n-BuLi) THF) Diethyloxalate (available from Aldrich).
Reaction sequence (a) depicts the preparation of 2_a-Scheme 4, wherein the
para-bromine moiety on resin-bound aryl silane intermediate 1-Schemg4 is
substituent X which is then modified by additional synthetic chemistry (such
as
creation of an alkyl lithium species in an aprotic solvent such as THF) to
give
Sc 4, wherein X is defined as shown in Scheme 4. Reaction sequence (b)
depicts the preparation of 2b-Scheme 4) wherein the para-bromine moiety on
resin-
bound aryl silane intermediate 1-Scheme 4 is substituent X which is then
modified
by additional synthetic chemistry (such as creation of an alkyl lithium
species in an
aprotic solvent such as THF) to give 2b-Scheme 4, wherein X is a carboxylic
acid
moiety. Reaction sequence (c) depicts the preparation of 2c-Scheme 4, wherein
the
para-bromine moiety on resin-bound aryl silane intermediate 1-Scheme 4 is
substituent X which is then modified by additional synthetic chemistry (such
as
creation of an alkyl lithium species in an aprotic solvent such as THF) to
give 2b-
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Scheme 4, wherein X is a ketoester moiety. The moieties A, B and C may be as
defined above.
Scheme 5
Scheme 5 illustrates additional synthetic chemistry that was successfully
performed in order to prepare an aromatic carbocycle (biphenyl) with a
hydrogen left
at the cleavage site, according to this invention.
\ p ~ \ / ~ Br
\ a
i
\ p ~ \ / ~ \
b
\ s
\ \
H
(a) Phenylboronic acid, (Ph3P)4Pd) Toluene, Ethanol; aq Na2C03; (b) TFA, Neat.
The resin-bound aryl silane intermediate 1-Scheme 5 (prepared similarly to
4-Scheme 1 ), wherein X is bromine, and A, B and C are hydrogen, is reacted
with
phenylboronic acid and (PhgP)4Pd (available from Aldrich) in a mixture of an
aprotic and a protic solvent to yield the resin-bound aryl silane intermediate
t-
he . Subsequent cleavage of resin-bound aryl silane intermediate 2-Scheme 5
under strong acidic conditions produces the aromatic carbocycle biphenyl) -Sch
me
5_. This key reaction is used according to this invention in order to
synthesize a
variety of biphenyls substituted with various functional groups with
conventional
chemistry that will be obvious to the skilled artisan. See, for example,
Scheme 10
below which illustrates the use of a substituted boronic acid in order to make
a
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substituted biphenyl (~-scheme 10). A review of boronic chemistry which is
compatible with the aryl silane bond, can be found in Suzuki, Acc. Chem.
Res.,15)
pp. 178-184 ( 1982). It will be obvious to one of ordinary skill in the art
that
additional synthetic chemistry may be similarly performed on resin-bound aryl
silane intermediates wherein X, A, B and C are, independently from one
another,
hydrogen, halogen, alkyl, alkenyl, alkynyl, alkoxy, aryloxy, thioether,
alkylthio, -
C{O)Ra, wherein Ra is hydrogen or alkyl, t-butoxyaminocarbonyl, cyano, nitro (-
N02), aryl, heteroaryl) arylalkyl, alkyl disulfide, aryl disulfide, acetal,
fluorenylmethoxy-carbonyl or orthoester (-C(OR)g, wherein R is C 1 to C4
alkyl),
provided that X, A, B and C can not a11 be hydrogen and X, A, B and C can not
all
be alkyl, and provided that the chemistry is compatible with modifying the
substituents without cleaving the aryl silane bond.
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Scheme 6
Br o
~o \ /
\ a
P I / I ~ O~S' \ I + I / >
Y' 'Q
1
O COOH
( \ o I \ ~ I I
/ / /~ ~ \ ~ Y'
P O Si
O Y"
\ ~O \ / \ ' >
P I / I / O ~Si \ I I / Y'
9~: Y"= NCO
~: Y"=NH
O NHCO(R 3)NH 2
\ ~O ' / \
P I/ I/ o~si \I ICY. >
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WO 98I17695 PCT/US97l19450
Scheme 6 (continued)
R3
N NH
\ ~O \ / \ a
I/ I/ o~s, \I ICY, >
R3 O
~NR'~
N
I \ o I \ / I I
/ /
R3 O
~NR4
N
\ I ( /Y.
(a) n-BuLi, THF) optionally substituted phthalic anhydride; (b) (i)
(Ph0)2P(O)N3)
Et3N, Toluene; (ii) NaOH) MeOH; (c) (i) peptide coupling; (ii) Deprotection
with
20% piperidine in DMF; {d) DMF) 5% acetic acid; (e) 4-benzyl lithium
oxazolidinone, THF, R4-Z; (f) TFA.
The resin-bound aryl silane intermediate 3-Scheme 6 is prepared using the
general procedure outlined above for preparing 2a-Sc eme 4, using optionally
substituted phthalic anhydride, wherein the optional substituent(s) is Y', and
Y' is
hydrogen, halogen, alkyl, alkenyl, alkynyl, alkoxy) aryloxy, thioether,
alkylthio)
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C(O)Ra, wherein Ra is hydrogen yr alkyl) t-butoxyaminocarbonyl, cyano, vitro (-
NOZ), aryl, heteroaryl, arylalkyl, alkyl disulfide, aryl disulfide, acetal,
fluorenylmeth-oxycarbonyl or orthoester {-C(OR)3, wherein R is C1 to C4
alkyl).
Additional synthetic chemistry known in the art is performed with eventual
preparation of an N-protected amino acid (preferably with an Fmoc protecting
group) compound. Peptide coupling is completed using well known published
procedures. As used herein) substituent R3 is hydrogen) halogen, alkyl)
alkenyl,
alkynyl, alkoxy, aryloxy, thioether) alkylthio, C(O)Ra) wherein Ra is hydrogen
or
alkyl, t-butoxyamino-carbonyl, cyano, vitro (-N02), aryl, heteroaryl
arylalkyl, alkyl
disulfide, aryl disulfide, acetal) fluorenylmethoxycarbonyl or orthoester (-
C(OR)3,
wherein R is C 1 to C4 alkyl). Deprotection of 4-Scheme 6 is accomplished with
conventional techniques (such as 20% piperidine in DMF) to produce 5-Scheme 6.
Cyclization of 5-Scheme 6 is accomplished with an organic acid (such as acetic
acid)
in an aprotic solvent (such as DMF) to produce 6-Scheme 6. Analogs of 6-Scheme
6
may be N-alkylated at the position-1 nitrogen of the benzodiazepine ring
(depicted
in the scheme as R4), using conventional techniques, for example, reaction
with a
base (such as 4-benzyl lithium oxazolidinone) in an aprotic solvent and
alkylation
with an alkyl halide or alkyl tosylate (such as R4-Z, wherein R4 is alkyl; and
Z is Br,
I or tosylate). Cleavage of the resin-bound aryl silane intermediate 7-Scheme
6 to
produce an optionally substituted aromatic carbocycle, i.e., the
benzodiazepine 8-
cheme 6, is accomplished by treatment with strong acid.
For purposes of illustration for this scheme, X is Br and A, B and C are
hydrogen. However, it will be recognized that further diversity may be placed
on
the end-product benzodiazepine if the substituents X, A, B and C on the
staring
material are as defined more broadly, above.
Scheme 6a
Using the alternative synthetic sequence depicted below, 4b-Scheme 6 may
be synthesized through a nitrobenzophenone intermediate.
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N02
O ( \ ~ ~ Br \ COCI
P / / O~Si \ ~- I / Y >
2
O N02
\ o
/ / /~, ~ \ ~ Y~ >
P O Si
3
O NHZ
\ ~O \ ~ \
P ~ / ~ / O~S' \ ( ~ / Y'
(a) n-BuLi, THF, 2-nitrobenzoyl chloride; (b) NaSH, THF, MeOH/water
Scheme 7
Scheme 7 illustrates a method for preparing 1,3- or 1,4-diaminobenzene
compounds,
one of the various types of aromatic carbocycles that may be prepared using
the
silane linkers of this invention:
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Br Br
\ a \ b
Br
Si Br
NO 2 NO 2
1 er
HO ~ /
/
Si
NO 2
Br
\ ~O ~ \ / ~ d
P / / O ~ Si
N02
4
NH 2
\ ~O ~ \ / a
P / / O /'~ li
r~ ~ NH 2
NHCOR 5
\
NHCOR s
(a) n-BuLi, THF) -105~C, BrCH2Si{Me)2C1; (b} {i) NaOMe, 4-hydroxybenzyl
alcohol, THF; (c) NaH, THF, Merrifield chloromethyl resin; (d) (i) NH3, MeOH;
(e} NaSH) THF, Water; (iii) Peptide coupling; (iv) TFA to cleave the aromatic
carbocycle while leaving a hydrogen at the cleavage site.
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In a manner similar to that described in Scheme 1, a substituted silane
intermediate of Formula (IIB), (i.e., 2-Scheme 77, wherein R" and R"' are
methyl; the
substituents X and A are bromine and vitro, respectively; B and C are
hydrogen; Y is
bromine; and n is l, is prepared by forming a lithium species of 2,4-
dibromonitrobenzene (Aldrich) and subsequent reaction with a silane compound
(such as bromomethyl chlorodimethyi silane available from Aldrich) in an
aprotic
solvent (such as THF or ether). The aryl silane intermediate of Formula (IIB),
wherein R" and R"' are methyl; substituents X and A are bromo and vitro,
respectively; B and C are hydrogen; Y is bromo; and n is 1 j2-Scheme 71, is
then
reacted with a strong base (such as sodium methoxide or potassium carbonate)
and
an optionally substituted benzyl alcohol in an aprotic solvent (such as THF,
dimethyl
formamide, dimethyl acetamide or DMSO if sodium methoxide is the base; acetone
or ethyl methyl ketone if potassium carbonate is the base) to prepare the aryl
silane
intermediate of 3-Scheme 7. This intermediate is coupled with a polymer resin
(such as Merrifield resin, Wang resin, or any other suitable resin described
herein) in
an aprotic solvent (such as THF) using a base (such as sodium hydride, sodium
methoxide in THF) dimethyl formamide, dimethyl acetamide or DMSO, or
potassium carbonate in acetone or ethyl methyl ketone) to produce 4-Schemg 7.
Additional synthetic chemistry, such as reduction of a vitro group to an amino
group, which will be obvious to one of ordinary skill in the art, is performed
in order
to modify the substituents X and A. Subsequent additional synthetic chemistry
may
be performed, such as N-acylation using various carboxylic acid derivatives
and
amino acids under standard conditions known in the art, to produce N-
substituted
resin-bound aryl silane intermediates 5-Scheme 6. Cleavage of the resin-bound
aryl
silane intermediate with strong acid conditions affords 6-Scheme 7, wherein
substituents B ) C, RS and R6 are, independently from one another) hydrogen,
halogen, alkyl, alkenyl, alkynyl, alkoxy, aryloxy, thioether, alkylthio, C(O
jRa)
wherein Ra is hydrogen or alkyl, t-butoxyaminocarbonyl) cyano, vitro (-N02),
aryl,
heteroaryl, arylalkyl, alkyl disulfide, aryl disulfide, acetal,
fluorenylmethoxycarbonyl or orthoester (-C(OR)3) wherein R is C1 to C4 alkyl).
Scheme 8
Scheme 8 illustrates a method for preparing amino carboxy compounds, another
class of aromatic carbocycles that may be prepared using the silane linkers of
this
invention:
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Br
p
P / / O ~Si
NO 2
i
COOH
I\ o I\ /I
P ~ / o ~si
NO 2
CONHR 7
\ ~O \ / c
P I / I / p ~s~ ~ I
NO 2
CONHR
\ w0 \ / d
!/ I/ ~\I \I
P O
NHCOR 8
CONHR ~
\
NHCOR a
(a} n-BuLi, THF and C02; (b) peptide coupling; (c) (i) NaSH) THF, Water; (ii)
peptide coupling; (iii) TFA, Neat.
In a manner similar to that described above for Scheme 7) resin bound aryl
silane intermediate 1-Scheme 8 is prepared. Additional synthetic chemistry is
performed on the intermediate in order to prepare amino carboxy aromatic
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WO 98I17695 PCT/US97/19450
carbocycles 4-Scheme 8. For example, when the substituent X of 1-Scheme 8 is
bromine, the bromine moiety is converted, by conventional techniques to a
carboxy
group, through an alkyl lithium species in an aprotic solvent (such as THF). 2-
Scheme 8 is converted to an amide using conventional peptide coupling
techniques
with various amines and amino acid derivatives. Additional synthetic chemistry
which would be obvious to the skilled artisan is performed in order to modify
the
substituents X, A, B and C, for example) N-acylation using various carboxylic
acids
and amino acids. Cleavage of the modified aromatic carbocycle in order to
prepare
the final product which is a compound of 4-Scheme 8, wherein the substituents
B, C)
R~ and R8 are) independently from one another) hydrogen, halogen) alkyl,
alkenyl,
alkynyl, alkoxy, aryloxy, thioether, alkylthio, C(O)Ra, wherein Ra is hydrogen
or
alkyl, cyano) t-butoxyaminocarbonyl, nitro (-N02), aryl, heteroaryl,
arylalkyl, alkyl
disulfide, aryl disulfide, acetal, fluorenylmethoxycarbonyl or orthoester (-
C(OR)g)
wherein R is C1 to C4 alkyl), is accomplished under strongly acidic conditions
(such
as treatment with TFA).
Scheme 9
Scheme 9 illustrates a method for preparing biphenyltetrazole compounds, yet
another class of aromatic carbocycles that may be prepared using the silane
linkers
of this invention.
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Br \ Br
/ ( Rs
Br CN ~ N
Br
N (' N
1
\ Br
b s
R
N c
Bra;
N
N 'N/
\ O / ~ \ Br d
I R s ~.
P / \ O /~.Si / N~
i
N-N
RsN_N~
Ria
(a) (i} NaN3) A1C13; (ii} Base, R9Z') wherein Z' is Cl) Br) I or tosylate; (b)
n-BuLi,
Ether, BrCH2Si(Me)2; (c) (i) NaOMe, 4-hydroxy benzyl alcohol; (ii) NaH, THF,
Merrifield chloromethyl resin; (d) (i) Pd(PPh3)4, 4-R1~-substituted
phenylboronic
acid [wherein Rl~ is aldehyde (-CHO), -CH20R, halogen, -CH(OR)2, -C(OR)3, -
N02, -NR2, -SR, (wherein R is C 1 to C4 alkyl), an ethylene dioxy group, or an
optionally substituted aryl group] Na2C03(aq), toluene, ethanol; (ii) TFA,
Neat.
2-Scheme 9 {wherein X and A are bromine and B and C are defined as
described above) prepared by reacting 1-Scheme 9 (prepared from 2,4-
dibromobenzoic acid which is available from Aldrich) by reaction with
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methanesulfonyl chloride and ammonia) with sodium azide in the presence of a
Lewis acid, and then N-alkylating the intermediate previously formed, using
conventional techniques, for example, reaction with a base (such as NaH,
potassium
carbonate or trialkylarnines) in an aprotic solvent, and alkylation with an
alkyl halide
or an alkyl tosylate (such as R9-Z', wherein R9 is alkyl; and Z' is Cl, Br, I
or
tosylate). 2-Scheme 9 is coupled with a silane compound and then with a
polymer
resin to prepare 4-Scheme 9) as described previously. Additional synthetic
chemistry is performed in order to modify the aromatic carbocycle bound to the
resin. Cleavage of the substituted aromatic carbocycle is accomplished using
strong
acid conditions. It will be clear that X and A can be other than bromide and
as
defined above, provided that X) A, B and C can not alI be hydrogen and not all
X, A)
B and C can be alkyl.
Scheme 10
Scheme 10 illustrates the preparation of an aromatic carbocycle 3-Scheme
10, wherein the carbocycle is an aldehyde substituted biphenyl compound. 1-
Scheme 10 is prepared according to Scheme 1 and then reacted with an
optionally
substituted boronic acid (such as 4-formylphenylboronic acid) in a basic
medium
(such as sodium carbonate) and an aprotic solvent (such as toluene) at
elevated
temperatures (such as 100~C) to give a resin-bound aryl silane intermediate 2-
Scheme 10. Cleavage of 2-Scheme 10 with TFA yields the aromatic carbocycle
with a hydrogen at the clevage site.
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\ O ~ \ / ~ Br a
~~ \
P O Si
1
CHO
\ ~O ~' / v b
f/ ~/
P 4 Si
CHO
a) 4-formylphenylboronic acid,( P~ P) 4Pd, Na2C~ (aq), Toluene, EtOH, 100~
b) TFA, neat, 25~
Scheme I1
Scheme 11 illustrates the preparation of an amine substituted biphenyl
compound using the resin-bound aryl silane intermediate 1-Scheme 11 (prepared
according to step (a) of Scheme 10 above) as a starting material. 1-Scheme 11
is
reacted with an optionally substituted primary amine (such as benzyl amine,
Aldrich
O, Milwauke, WI ) in an aprotic or erotic solvent (such as toluene, methylene
chloride, ethanol or methanol) to give a resin-bound aryl silane intermediate
substituted with a benzyl imine (2-Scheme 11 ). Suitably, the optionally
substituted
primary amine is substituted with alkyl, aryl heteroaryl, arylalkyl or
heteroarylalkyl;
preferably arylalkyl; more preferably, benzyl. Additional synthetic chemistry,
specifically a Grignard reaction using allylmagnesium bromide (made
conventionally) in an aprotic solvent (such as ether and toluene), is
performed on
resin-bound aryl silane intermediate 2-Scheme I 1 to convert the benzyl imine
to 3-
Scheme 11, an aminobenzyl substituted alkenyl moiety. Compounds analogous to
3-Scheme 11, but wherein the alkenyl moiety is varied, may be prepared
prepared by
using a different Grignard reagent under the same reaction conditions.
Standard
cleavage conditions are used to give 4-Scheme 11.
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cHo
( \ O ~ \ / ~ \ a
P / / O BSI
/ ~ ~N i \
\ a ~ \ / ~ \ /
b
P / / O ~Si \
i ~ \
t
\ o_~\
P / / o ~si
3
H
\ I ,N I /
I /
a) PhCI-~ NH 2 , Toluene ; b) AIIyimagnesium bromide2~, Toluene, 25~; c) TFA
(neat)
Scheme 12
Scheme 12 illustrates the preparation of another substituted biphenyl
compound using the resin-bound aryl silane intermediate 1-Scheme 12 (prepared
according to step (a) of Scheme 10 above) as a starting material. In this
case, the
aldehyde substituted resin-bound aryl silane intermediate 1-Scheme 12 is
reacted
with an optionally substituted Wittig reagent (such as phosphorane or a
compound of
the formula Ph3P=CHCOORb, wherein Rb is C 1 to C6 alkyl, specifically ethyl)
in
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WO 98l17695 PCT/US97119450
an aprotic solvent (such as TI3F, ether or dioxane) at elevated temperatures
(such as
60~C) to give resin-bound aryl silane intermediate 2-Scheme 12. The vinyl
ester 2-
scheme 12 is modified to a thiol addition moiety by reaction with an
optionally
substituted thiol (such as thiophenol, Aldrich) in a tertiary amine base (such
as
triethylamine) in an aprotic or protic solvent (such as toluene or ethanol) to
give
resin-bound aryl silane intermeidate 3-Scheme 12) which intermediate is
cleaved to
give the desired derivatized aromatic carbocycle, 4-Scheme 12. It will be
recognized
that various additional synthetic chemistry can be performed on intermediate 2-
Scheme 12 in order to derivatize across the alkenyl bond, for example by
performing
a Wadsworth-Emmons reaction as disclosed by Patios, Tet. Lett., p. 1317 ( 1991
);
Coatrot, Synthesis, p. 790 ( 1956); Marshall, J. Org. Chem., 51( 10)) p. 1735
( 1986);
and Mandai) Tet. Lett., 21 pp. 2987-2990 ( 1992).
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CHO
\ O \ / ~ a
P O Si
1
COOEt
/ ~ b
P O Si
2
COOEt
~O ~ c
P ( / ~ / O~Si
3
4
a) Phg P=CHCOOEt, THF, 80~; b) PhSH, ~N, Toluene, 25~ ; c) TFA, Neat
Schemes 13a and 13b
Schemes 13a and 13b illustrate other types of additional synthetic chemistry
which are compatible with the aryl silane bond of various resin-bound aryl
silane
intermediates.
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\ CoR
I \ o I \ / I \ a
/ / /~~ \
p O Si
1 a R= OEt
1b R= Chi
\ COR
\I
I\ V
2a R= OEt
2b R=CI-i,~
a) TFA, Neat
Scheme 13 a
\ COCIi~
I \ O I \ / I \ a
/ ~~ \
p o s,
1
\ w0 \ -r
P ( / I / O ~Si
2
Scheme 13
a) PhSH, E~ N, Toluene; b) TFA, Neat
_q.4_
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Scheme 14
Scheme 14 merely illustrates the standard reaction conditions for making
dibromobenzonitrile (starting material 1-Scheme 15).
Br Br
\ COOH CONK
a \
Br
Br
1 2
Br
CN
b
s
Br
3
Schemes 1S and 16
Scheme 15 illustrates the reaction conditions for making a cyano) bromo-
substituted aryl silane compound 4-Scheme 15. Scheme 16 illustrates the
preparation of a resin 2-Sc eme 16) starting from the Merrifield chloromethyl
resin
1-Scheme 16.
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Br
Br
\ CN
a ~ CN
b
Br
-SI ~Br
1
2
Br
CN CN
/ ~ /
- ~ ~OAc - ~ OOH
3 4
Scheme 15
a) n-BuLi, THF, -105~,BrC~ISI(Me~Ct; b) NaOAc, DMF, 50~
c) HCI (3 N)) MeOH) 25~
/ OH
CI
a ~ \ 0 \
/ /
P P
2
1
Scheme 16
a) Ke CO~ , DMF, hydroqulnone, 60~
Scheme 17
Scheme 17 illustrates the preparation of a cyano-substituted aromatic
S carbocycle using the cyano, bromo-substituted aryl silane compound 2-Scheme
17
(prepared per Scheme 15) and resin 1-Scheme 17 (prepared per Scheme 16) as
starting materials. As used herein, 'Ph3P" is triphenylphosphine (Aldrich);
"DEAD"
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is diethylazodicarboxylate (Aldrich); and "NMM" is N-methyl morpholine
(Aldrich).
/ OH Br
\ O \ I \ CN a
I / + ( /
P ''~
- ~~OH
2
/ O~Si \ CN b
\ ~ ~ I /
~O Br
P 3
/ I O~Si I \ CN
c
I \ p \ /
P / 4 / CHO
i
/ O ~Si \ CN
\ ( ~ I /
\ ~o \ /
I / L ~ ~N \ I
P
a) Pi~P, DEAD) NMM, 35~ b) 4-formylphenylboronic acid, ~P~I)4Pd, N~ CO~ (aq)
EtOH, Toluene, 100~
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It will be recognized that when the silane linker contains benzylic groups,
these groups may be cleaved under acidic conditions) such as with TFA. With
respect to chemical transformations of increased complexity, cleavage of the
benzylic groups could lead to undesired side products. When preparing a
combinatorial library, these side products are particularly undesireable.
Therefore,
the instant invention includes a silane linker of formula D-CH2-Si-R"R"',
wherein D
is -(CH2)3-, i.e., -(CH2)4-Si-R"R"', as an appropriate silane linker to carry
out solid
phase synthesis of increasing complexity, particularly when the possibility of
undesired side products upon cleavage of the final product from the resin-
bound aryl
silane intermediate, exists.
Scheme 18
Scheme 18 illustrates the preparation of a resin-bound aryl silane
intermediate 3-Sche e18_, utilizing an all carbon silane linker of formula D-
CH2-Si-
R"R"', wherein D is -(CH2)3-, i.e.) -(CH2)q.-Si-R"R"', wherein R" and R"' are
each
methyl.
'cl a)
w I w
2
b) ~ li
3
I
I-H
Reagents and Conditions: a) allylmagnesiumbromide) toluene, 90~C; b) \ I
ptCl2~phCH=CH2)2, Toluene
Br
Scheme 18(a)
Scheme 18(a) illustrates the preparation of 2-Scheme 18(a) which is a
reagent used in the preparation of 3-Sche a 18, described above.
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/ Br a) ' Si H
Br
Br
2
Reagents and Conditions: a) n-BuLi, THF, -78~C; CI(Me)2SiH
Scheme 19
Scheme 19 illustrates the preparation of a sulfonamide aromatic carbocycle
f6-Scheme 19) using 3-Scheme 18 (i.e., I-Scheme 19) as the starting material.
0
i
H
I ~ I a) I
Br i
I
1 si
2
I w wN ~ I
i
b) ( I c)
ji 3
N ~ d)
I / H ~ I ~ I i' I
i Ts~
I v
si
4 S!
N
I
~ I i Ts
s
Reagents and Conditions: a} 4-formyiphenylboronic acid, (Ph3P)4Pd, Na2C03,
EtOH, Toluene, 90~C;
b)PhCH2NH2, Toluene, 70~C;
c)Na(OAc)38H, CH2C12
d)TsCI, Pyridine
e)TFA: DMS: H20
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Scheme 20
Scheme 20 illustrates the use of an acid labile MOM protecting group with
the all carbon silane linker. The usefullness of this reaction scheme is the
demonstartion that 10% TFA is useful in deprotecting 2-Scheme 20, however, 10%
TFA does not cleave the aromatic carbocycle from the resin-bound aryl silane
intermediate 3-Scheme 20.
b)
P ~.Si ~ ( OH
3
Reagents and Conditions: a) ~ I oMOM
oH~z , Pd(Ph3P)4, Na2C03, EtOH, Toluene, 90~C;
b) 10% TFA In CH.ZCL2
Without further elaboration, it is believed that one skilled in the art can,
using the preceding description, utilize the present invention to its fullest
extent.
The following examples further illustrate the synthesis and use of the
compounds of
this invention. The following examples are, therefore, to be construed as
merely
illustrative and not a limitation of the scope of the present invention in any
way.
EXAMPLES:
Preuaration of 4-bromonhenvldimethvlsilvlmethvlbromide (2-Scheme 1)
A solution of n-butyllithium (2.5M, 53 mL, 0.133 mole) was added dropwise over
30 minutes under argon to a solution of 1,4-dibromobenzene (30.0 g, 0.127
mole) in
dry THF (575 mL) at -78oC. After stirring for 1.5 h,
bromomethylchlorodimethylsilane (25.0 g, 0.133 mole) was added to the reaction
mixture through a canula and the solution was stirred for 1.5 h at -78oC. The
reaction was poured into water (325 mL) and extracted with ether. The combined
extracts were washed with water and brine, and then dried
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(Na2S04) and concentrated in vacuo to an oil. The oil was distilled
(Kugelrohr,
110-125~C, .05 mm Hg) to afford the compound as a clear, colorless oil (22.6
g,
58%). 1H NMR (400 MHz, CDCl3) 7.45 (dd, 4H)) 2.60 (s, 2H), 0.45 (s) 6H).
Preparation of 4-t4-bromophenvldimethylsilylmethvloxy)benzvl alcohol
(Formula 3-Scheme 1)
Sodium methoxide (4.17 g, 73.4 mmole) was added under argon to a solution of 4-
hydroxybenzyl alcohol (8.67 g, 69.9 mmol) in dry DMF (70 mL) and the reaction
mixture was stirred for 30 minutes at room temperature. 4-
Bromophenyldimethylsilylmethyl-bromide (22.b g) 73.4 mmol) was added through a
canula and the reaction was stirred at RT for 30 minutes and at 65~C for 45
minutes.
The reaction was poured into ice water (250 mL) and extracted with ethyl
acetate.
The combined extracts were washed with water, 5% sodium bicarbonate and brine
and the dried (Na2S04). The solution was concentrated to an oil at reduced
pressure
and purified by flash chromatography (silica gel, 20% ethyl acetateihexane) to
yield
the product as a clear) colorless oil (9.23 g, 38%). 1H NMR (400 MHz, CDC13)
7.48
(dd, 4H), 7.I0 (dd, 4H), 4.61 (s, 2H), 3.77 (s, 2H), 0.42 (s, 6H).
Preparation of resin-bound aryl silane intermediate 4-Scheme I
A solution of 4-(4-bromophenyldimethylsilylmethyloxy)benzyl alcohol (7.22 g,
20.55 mmol) in dry THF (5 mL) was added to a suspension of sodium hydride
(95%,
0.6l7 g, 25.69 mmol) and stirred at 30~C until gas evolution ceased.
Merrifield
resin (Nova Biochem.) 1.4 mmol/g)) was added with additional dry THF ( 15 mL)
and the reaction mixture was stirred at 65 to 70~C for 24 h. The reaction
mixture
was cooled to room temperature and quenched with methanol (5 mL) and the resin
was filtered and washed with methanol, methanol/water ( 1:1 ), methanol)
methylene
chloride and finally methanol. The product was dried in vacuo for 24 h to
yield the
title compound (8.99 g). Anal. found: C) 82.20; H) 7.03; Br, 6.67.
Preparation of Formula 2-Scheme 2
Wang resin (2.0 g), prepared pursuant to Su-Sun Wang, JACS, 95, p. 1328
(1973), is
suspended in THF( 15 mL) and allowed to swell for 30 minutes. Sodium
hydride(250 mg) was then added in one portion and stirred at room temperature
for
2h. Dibromide (2 g) was added, followed by tetra-n-butylammonium iodide and
heated under reflux for 4 days. The reaction mixture was cooled and carefully
quenched with the addition of methanol {5 mL). Filtration followed by washing
with methanol, water, methylene chloride and finally with methanol yielded the
resin which was dried in vacuum oven. Anal.: Br (4.7%), MS(DCI) NHg) 380; 349
and 351 peaks equal intensity.
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Bromination of resin-bound arvl silane intermediate 4-Scheme 1 (See Scheme
Resin-bound aryl silane intermediate 4-Scheme 1 (0.5 g) was swelled in
methylene
chloride(5 mL). Bromine(0.1 mL) was added and stirred overnight. Reaction
mixture, after filtering, washing with ether and removal of solvents in vacuo,
gave
an oil ( 175 mg) which solidified on standing. It was found to be
dibromobenzene by
1 H NMR and m. pt.
1H NMR (CDCIg, 400 MHz) d ?.35(s); m. pt. 86-88~C.
Reaction of resin-bound arvl siiane intermediate 4-Scheme 1 with HBr (See
Scheme 3(c))
Resin-bound aryl silane intermediate 4-Scheme 1 (500 mg) was suspended in
methylene chloride (5 mL). Gaseous HBr was then passed through the suspension
cooled in an ice bath for 5 minutes. The cooling bath Was removed and the
reaction
mixture stirred for 30 minutes. Excess HBr was purged from the suspension by
passing Argon until no HBr was detected with pH paper. The resin was filtered
off,
washed with ether and the solvents removed in vacuo to give 230 mg of an oil.
MPLC (silica) ethyl acetate: hexane 1:10) provided the product. MS (DCI) NHg)
428 (M+ +NH4).
Reaction resin-bound arvl silane intermediate 4-Scheme 1 with trifluoroacetic
acid (See Scheme 3(a))
Resin-bound aryl silane intermediate 4-Scheme 1 (500 mg} was stirred in
trifluoroacetic acid (2 mL) and the product was analyzed by GCSE-30, 50~C)
room
temperature 5.14 minutes. The formation of bromobenzene was confirmed by co-
injection with authentic bromobenzene.
Preparation of resin-bound arvl silane intermediate 2a-Scheme 4
A solution of n-butyllithium ( 1.6M, 4.0 mL, 6.4 mmole) was added dropwise to
a
suspension of the resin-bound aryl silane intermediate 4-Scheme 1 (2.0 g, 2
mmole)
in dry THF (22 mL) at lOoC and the suspension was stirred for 2.5 h at room
temperature. Phthalic anhydride ( 1.18 g, 8 rnmol) dissolved in warm THF (6
mL)
was added and the suspension was stirred for 1 h at RT. The resin was filtered
and
washed with THF, THF/water (2:1 ), THFI2N HCl (3:1 ), THF/water (2:1 ), water,
THF/water (2:1 ), THF and methanol. The product was dried in vacuo for 24 h at
50oC to yield the title compound (1.91 g). Anal. found: C, 85.47; H, 7.32. IR
(KBr)
1718 cm-1 and 1698 cm-1 (carbonyl stretch).
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Preparation of resin-bound arvl silane intermediate 2b-Scheme 4
In the same manner as described for resin-bound aryl silane intermediate 2a-
Scheme
4_) the resin-bound aryl silane intermediate 4-Scheme 1 (0.5 g, 0.5 mmole) in
dry
THF (6 mL) was treated with a solution of n-butyllithium ( 1.6M, 1.0 mL, 1.6
mmole) followed by solid carbon dioxide to give the carboxy resin-bound aryl
silane
intermediate 2b (0.277 g). Anal. found: C, 85.65; H, 7.55. IR (KBr) 1694 cm-~
(carbonyl stretch).
Preparation of resin-bound arvl silane intermediate 2c-Scheme 4
In the same manner as described for resin-bound aryl silane intermediate 2a-
Scheme
4, the resin-bound aryl silane intermediate 4-Scheme 1 (0.5 g, 0.5 mmole) in
dry
THF (6 mL) was treated with a solution of n-butyllithium ( 1.6M, 1.0 mL, 1.6
mmole) followed by diethyl oxalate (0.34 mL, 2.5 mmol) to give the glyoxylic
ester
resin-bound aryl silane intermediate 2c {0.330 g). Anal. found: C, 85.75; H,
7.53. IR
(KBr) 1735 cm-1 and 1685 cm-1 (carbonyl stretch).
Palladium couplins of resin-bound arvl silane intermediate 4-Scheme 1 with
phenylboronic acid and cleavage with TFA to produce biphenyl ,See Scheme 5)
Resin-bound aryl silane intermediate 4-Scheme 1 (2 g) was suspended in toluene
( 15
mL) and allowed to swell for 30 minutes. To this was added
tetrkistriphenylphosphine (275 mg, 0.25 mmol), phenylboronic acid (500 mg, 4.1
rnmol)) ethanol (2 mL), sodium carbonate, aq (2 mL, 2M), all of which was
heated
in an oil bath maintained at 90~ for 16h. The reaction mixture was cooled,
filtered
washed with methanol, water, methylene chloride and methanol to give a black
solid
which was taken for the next step. A portion of the above resin ( 1 g) was
treated
with trifluoroacetic acid ( 3 mL) and stirred at room temperature for 24 h.
Methylene chloride ( 10 mL) was added and filtered, washed with methylene
chloride. Removal of solvents gave a slight brown oil which was triturated
with
hexane (50 mL). Evaporation of the hexanes yielded biphenyl (78 mg) which was
compared with an authentic sample.
Reaction of resin-bound arvl silane intermediate 2a-Scheme 4 f also 3-Scheme
61
with diphenylphosphorvl azide to prepare 4-Scheme 6
The resin-bound aryl silane intermediate 2a-Scheme 4 was suspended in toluene
and
allowed to swell for 30 minutes. To this was added diphenylphosphoryl azide
and
the mixture is heated in an oil bath maintained at 90~C for 16 h. The reaction
mixture was cooled and filtered) washed with methanol, methylene chloride,
methanol and finally dried in vacuo to give the isocyanate. IR 2100 cm-l.
Hydrolysis of resin-bound aryl silane intermediate Formula 4-Scheme 6 in
order to prepare resin-bound aryl silane intermediate Formula 5-Scheme 6
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The resin-bound aryl silane intermediate obtained above [4-Scheme 61 was
suspended in dioxane and refluxed with aqueous sodium hydroxide overnight.
Filtration followed by washing with methanol, water, methylene chloride and
finally
methanol provided the free amine.
Coupling of amino acid with resin-bound aryl silane intermediate Formula 5-
Scheme 6 to urenare resin-bound aryl silane intermediate Formula 6-Scheme fi
The amine resin-bound aryl silane intermediate 5-Scheme 6 was suspended in DMF
and allowed to react with FMOC-amino acid fluoride in the presence of 4-methyl-
2,6-di-tert-butylpyridine overnight. The resin-bound aryl silane intermediate
was
filtered, washed with methanol, DMF, methylene chloride and methanol. Drying
in
vacuo yielded the coupled product.
Denrotection and Cyclization of resin-bound aryl silane intermediate Formula
6-Scheme 6 to urepare resin-bound aryl silane intermediate Formula 7-Scheme
6
The above resin-bound aryl silane intermediate 6-Scheme 6 was suspended in DMF
and allowed to react with piperidine to give the free amine. The reaction
mixture
was filtered and washed as usual to provide the resin-bound aryl silane
intermediate
free amine. The resin-bound aryl silane intermediate free amine was suspended
in
DMF and heated at 60~ with 5% acetic acid to provide the cyclic product. See,
Bunin, B.A., Ellman, J.A., JACS, p. 10997 (l992).
Preparation of the nitrobenzonhenone resin-bound arvl silane intermediate (3-
Scheme 6
1-Scheme 1 (1.0 g) 1.0 mmol) was suspended in THF (10 mL) and cooled to -78~C.
Added n-BuLi (1.6 M in Hexanes, 1.6 mmoi) and allowed to react for 2 h. The
mixture was warmed to -65~C; 2-nitrobenzoyl chloride {1 mL, 7 mmol} was added,
and the mixture was allowed to warm to room temperature overnight. Filtration
followed by washing with methanol (3x25 mL), water (2x25 mL, methylene
chloride (2x25 mL and finally with methanol (50 mL) gave the resin which was
dried at 60~C in vacuo. Recovered ( 1.0g). IR 1740, 1520 cm-t.
Preparation of the aminobenzophenone resin (4-Scheme 6)
A mixture of nitrobenzophenone resin, 3-Scheme 6, (950 mg), NaSH ( 1.0 g) in
THF
( 10 mL), MeOH (5 mL), water (5 mL) was heated in an oil bath at 70~C for 16
h.
The mixture was cooled, filtered and washed with methanol, water, methylene
chloride and finally with methanol. Drying at 60~( in vacuo gave a slight
yellow
resin. Recovered (900 mg). IR 1640 (broad).
Preparation of 4-formvlbiphenvlsilane resin (2-Scheme 10l
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The bromoresin 1-Scheme 10 ( I g, 1 mmol) was swelled in toluene ( 10 mL) and
ethanol (4 mL). To this was added 4-formylphenylboronic acid (450 mg, 3 mmol),
aqueous sodium carbonate {2 M, 3 mL, 6 mmol) and tetrakistriphenylphosphine
palladium ( 200 mg). The reaction mixture was heated under Argon ("Ar") with
stirring for 24 h., cooled and filtered through a sintered glass funnel.
Washed the
resin with methylene chloride, methanol) methanol-water ( 1:1 ), methanol,
methylene
chloride and finally with methanol. Dried in vacuo to give colorless 4-
formylbiphenyl resin 2-Scheme 10. IR (KBr) l701 cm-1 (CHO).
Preparation of the Imine !2-Scheme lIl
The resin aldehydel-Scheme 11 made as described above (250 mg) and benzyl
amine (1 mL) in toluene (5 mL) was stirred at 25~C for 12 h. It was then
briefly
heated for 5 min at b0~C, cooled, filtered and washed with toluene followed by
diethyl ether. Dried in vacuo to give 2-Scheme 11 as a colorless solid. IR
(KBr)
1643 cm-1 (C=N). Anal C (87.64)) H(7.48)) N(0.99).
Addition of allvlmagnesium bromide to 2-Scheme 11 to give !3-Scheme 111
2-Scheme 11 (250 mg) was swelled in 1:1 ether, toluene {4 mL). To this at 25~C
was added allyl magnesium bromide) a conventionally made Grignard reagent,
(lmL, 1M in ether) and stirred overnight. Filtered, washed with ether, toluene
and
finally with ether. Dried in vacuo to give a colorless resin. IR (KBr) 1640 cm-
1
(C=C).
TFA cleavage of Amine !4-Scheme 111
3-Scheme 11 ( 100 mg) was stirred with trifluoroacetic acid (2 mL) for 12 h.,
filtered
and washed with methanol. Removal of solvents in vacuo followed by stirnng
with
saturated sodium carbonate and extracting into ether provided the biphenyl
derivative 4-Scheme 11.
1 HNMR (CDCl3, 400 MHz) S 7.2-7.8 (m, 14 H)) 5.7 (m, 1 H), 5.1 (m, 2H), 3.5-
3.8
(m, 3 H), 2.5 (bs, 2H). MS (M+H) 314.
Preuaration of the WlttlQ adduct !2-Scheme 127
Aldehyde resin 1-Scheme 12 prepared as above for 2-Scheme 10 (210 mg) was
swelled in THF (3 mL), added phosphorane (3S0 mg) and heated in an oil bath
maintained at 60~C for 24 hr. Cooled, filtered, washed with methanol,
methylene
chloride and finally with methanol. Dried in vacuo to give a colorless resin 2-
Scheme 12. FT-IR (KBr) 1708, 1636 cm-1.
Addition of thiophenol. Preparation of the sulfide !3-Scheme I21
The ester resin 2-Scheme 12 (200 mg) was swelled in THF (3 mL) added
triethylamine (0.2 mL) and thiophenol (0.3 mL) and stirred at 25~C for 2 days.
Filtered, washed with methanol) methylene chloride and finally methanol.
Drying in
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vacuo provided a colorless solid 3-Scheme 12. FT-IR (KBr) 1735 cm-1. Anal C
84.75,H7.21,52.11.
Cleava:=e of biphenylsulfide by TFA (4-Scheme 12)
3-Scheme 12 (20 mg) was taken up in a small test tube and exposed to TFA
vapors
in a dessicator for 24 h. Excess TFA was removed in vacuo and the product
extracted into diethyl ether. Removal of solvents provided the sulfide 4-
Scheme 12.
MS (M+H) 363.
TFA Cleavage of the ester (2a-Scheme 13a)
2-Scheme 12 (40 mg) was taken in a test tube and exposed to TFA vapors in a
dessicator for 24 h. Excess TFA from the resin was removed in vacuo and the
product extracted into ether. Removal of solvents provided 2a-Scheme 13a which
was found to be pure by 1 HNMR (CDC13, 400 MHz}
Addition of triphenvlphosphoranilidine acetone to aldehvde (lb- Scheme 13a)
1-Scheme 12 was swelled in THF ( 10 mL) and added phosphorane ( 1.4 g) and
heated at 60~ for 24 h. Cooled, filltered and washed with MeOH, CH2C12 and
finally with MeOH.
Dried in vacuo to provide the ketone.
FT-IR
Preparation of the dibromoamide (2-Scheme 14)
To a solution of dibromobenzoic acid (21.6 g, 77.2 mmol) in dry pyridine ( 150
mL)
under Ar was added methanesulfonyl chloride (9.28 g, 81 mmol) and stirred at
0~C
for 1 h. To this reaction mixture was passed ammonia gas for 10 min at 0~, and
then
poured into ice cold water (750 mL). The solid was filtered, washed with
water. Air
dried to give the amide (15.9 g, 74~l0). IR (neat) 3366, 3185, l650 cm-1. 1
HNMR
(CDCl3, 400 Mhz) b 7.72 (d, 1 H,J= 3Hz), 7.48 (d, 1 H, J= 7Hz), 7.42 (dd, 1 H,
J= 3,
7 Hz).
Preparation of the nitrile (3-Scheme 14)
To a solution of DMF (3.3 mL, 42.4 mmol) in dry CH3CN ( 100 mL) at 0~C was
added dropwise oxalyl chloride (3.6 rnL, 40.8 mmol) over 5 min. After stirring
for 5
min at 0~C, a solution of the amide (5.58 g, 20 mmol) in dry DMF (30 mL} was
added via canula. After S min, pyridine (6.5 mL, 80 mmol) was added over 1 min
and the reaction mixture was stirred at 0~C for 15 min. It was then poured
into
saturated NH4C1( 200 mL), extracted with 1:1 ethyl acetate: hexane (300 mL).
The
organic layer was washed with water (2x 100 mL), brine (75 mL) and dried over
anhydrous Na2S04. Removal of solvents followed by trituration with hexane
provided 3-Scheme 14 (4.68 g, 90%). IR (Neat) 2225, 1570, 1256 cm-1. 1 HNMR
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(CDCI3, 400 MHz) S 7.75 (d, 1H, J= 2 Hz)) 7.58 (dd) 1H, J= 2, 7 Hz), 7.55(d,
1H, 3=
7Hz).
Preparation of the bromocyanosilane (2-Scheme 15l
To a solution of 3-Scheme 14 (5 g, 19.2 mmol) in dry THF (200 mL) at -I05~C
was
added under Ar, n-BuLi ( 1.6 M in hexane, 12 mL) 19.2 nurlol) over a period of
30
min. The reaction mixture was then stirred for 10 min at -l05~C. To this was
added
bromomethylchlorodimethyl silane (4.67 mL, 24.9 mmol) over 2 min and stirred
for
45 min while warming to -80~C. The reaction mixture was poured to water (200
mL), extracted with 1:1 ether: hexane (200 mL), washed with water, brine and
dried
over anhydrous sodium sulfate. The resuling oil was flash chromatographed
(silica)
ethyl acetate(3%) in hexane) to give the 2- Scheme 15 (5.01 g, 79%).
1 HNMR (CDCl3) 400 MHz) d 7.9 (d, 1H, J= 2Hz), 7.75 (dd, IH) J= 2) 7 Hz), 7.5
(d) IH, J= 7 Hz), 2.8 (s) 2H), 0.5 (s, 6 H).
Preparation of the Acetate (3-Scheme 15)
To a solution of the 2-Scheme 15 (5.0l g, 15 mmol) in dry DMF (50 mL) was
added
anhydrous sodium acetate (3.70 g, 45.1 mmol) and stirred at 55~C for 16 h.
Cooled)
poured into ice water) extracted with 1:1 hexane, ether) wsahed with water)
brine and
dried over anhydrous Na2S04. Removal of solvents followed by flash
chromatography ( silica) ethyl acetae: hexane 1:19) gave the 3-Scheme 15 (
3.42 g)
73 %). 1 HNMR (CDC13, 400 MHz) 8 7.85 (d, 1H) J= 2Hz), 7.75 (dd, J= 2) 7 Hz),
7.5 (d, 1H, J= 7 Hz), 4.1 (s) 3H)) 2.0 (s, 2H)) 0.5 (s, 6 H).
Preparation of the alcohol (4-Scheme 15)
To a solution of the ~-Scheme 15 (0.79 g, 2.53 mmoI) in methanol (20 mL) was
added HCl (3 N, 4 mL) and stirred for I2 h. The reaction mixture was
neutralized by
the addition of solid sodium bicarbonate, filtered and solvents evaporated.
Diluted
with. ethyl acetae, washed with water, brine, dried. Removal of solvents gave
an oil
(0.68 g, l00%). IR(neat) 3421, 2226, 1570, 1254 cm-1. 1HNMR (CDCl3, 400
MHz) b 7.85 (d, 1H, J= 2Hz), 7.72 (dd, 1H, J= 2, 7 Hz)) 7.55 (d, 1H, j= 7 Hz),
3.75
(s) 2 H), 0.5 (s, 6 H).
Preparation of the phenol resin ~2-Scheme 167
To a suspension of Merrifield chloromethyl rein (20 g) 24.8 mmol) in dry DMF
(200
mL) was added hydroquinone (21.84 g, 198 mmol) followed by soilid K2C03
( 15.44 g) 112 mmol). The reaction mixture was heated in an oil bath
maintained at
65~C for 48 h., cooled, added ethanol (40 mL) followed by gradual addition of
2:1
EtOH: 3N HCl. The resin was filtered, washed with ethanol, ethanol:3N HCi,
EtOH, THF, MeOH) water, THF and finally with methanol. Dried in vacuo to give
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CA 02269737 1999-04-23
WO 98I17695 PCTlUS97J19450
2-Scheme 15 (20.8 g). IR (KBr) 3544, 3429, 1196, 1025 cm-1. Anal: C (89.55), H
(7.31)) Cl (0.20).
Mitsunobu counlin~of phenol resin (3-Scheme 1'7Z
To a solution of the alcohol ( 1 g, 3.7 mmol) in N-methylmorpholine (5 mL) at
0~C
was added triphenylphosphine (0.971 g, 3.7 mmol) and stirred for 5 min. To
this
was then added dropwise diethylazodicarboxylate (0.58 mL, 3.7 mmol) and
stirred at
0~ for 30 min. The resin ( 1 g) 1.24 mmol) was added, temperature increased to
35.
After 4 days, the product was filtered, washed with THF) MeOH and dried at 50~
in
vacuo to give 3-Schemel7 (Z.023 g). IR 2225 cm-~ {CN)
Preparation of butenvl r~olvstyrene (2-Scheme 18l
To chloromethyl polystyrene ( 12.0 g) 2 mmollgm) 1 ~lo cross linked) in
toluene (200
mL) was added allylmagnesium bromide (50 mL) 1M in diethyl ether). The
reaction
mixture was agitated by bubbling Argon through the solution and heated in an
oil
bath maintained at 90~ C for 16 h. Cooled, added saturated ammonium chloride
and
stirred for 30 min. The resin was filtered, washed with water, methanol and
dichloromethane.
Preparation of the resin-bound aryl silane intermediate (3-Scheme 18l
To butenyl resin (2 g) in toluene ( 15 mL) was added bisstyrenylplatinum(II)
chloride
(200 mg) and 4-brornophenyldimethylsilane (2 g). The reaction mixture was
agitated by bubbling Argon through the solution and heated in an oil bath
maintained at 95~C for 16 h. The reaction mixture was cooled, resin was
filtered,
washed with dichloromethane to give the product as a black material.
1 HNMR (MAS, Varian, 400 Mhz) d 7.45 (s, 2H), 7.25 (s, 2H), 2.4{bs) 2 H), 0.5
(s,
2H), 0.1 (s, 6H).
Preuaration of the binhenylcarboxaldehvde via Suzuki Reaction (2-Scheme 191
To resin-bound aryl silane intermediate (3-Scheme 18, i.e., l-Scheme 19) ( 2g,
4
mmol) in toluene(30 mL) was added tetrakistriphenylphosphinepalladium (300 mg)
followed by 4-formylphenylboronic acid ( 1.2 g) 8 mmol), ethanol (8 mL) and
sodium carbonate (aq) 2 molar, 8 mL). The reaction mixture was agitated by
bubbling Argon through the solution and heated in an oil bath maintained at
95~C
for 16 h. Cooled, washed with dichloromethane, methanol, water, methanol and
finally with dichloromethane to give product as a black solid (2.2 g).
1 HNMR (MAS)
Preuaration of the resin-bound arvl silane imine intermediate f3-Scheme 19l
To biphenylcarboxaldehyde resin ( 1 g) in toluene ( 10 mL) was added benzyl
amine
(3mL) and heated to 65~C for 10 h. Cooled, filtered and washed with
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WO 98l17695 PCTIUS97119450
dichioromethane. The resulting resin-bound aryl silane intermediate (3-Scheme
19)
(1.1 g) showed characteristic 1 HNMR(MAS).
Reduction of the imine by sodium triacetoxyborohydride: Preparation of amine
bound resin (4-Scheme 19)
To 3-Scheme 19 in dichloromethane was added sodiumtriacetoxyborohydride, The
reaction mixture was agitated by bubbling Argon through the solution for 24 h.
This
was followed by the addition of saturated sodium bicarbonate (5 mL) and
further
agitation for 2 h. The resin was filtered, washed with water, methanol and
dichloromethane. FT-IR (disappearance of peak at 1640 cm-1 ).
Preparation of the resin-bound arvl silane sulfonamide intermediate l5-Scheme
To the resin-bound aryl silane intermediate 4-Scheme 19 in pyridine was added
p-
toluenesulfonyl chloride and agitated by bubbling Argon through the reaction
mixture for 24 h. The resin was filtered, washed with dichloromethane,
methanol
and dichloromethane to provide the resin-bound aryl silane intermediate 5-
Scheme
19 as a blackish material. 1 HNMR (MAS).
Cleavage of the resin-bound arvl silane sulfonamide intermediate (6-Scheme
The resin-bound aryl silane intermediate S-Scheme 19 was treated with
TFA:DMS:H20 (90:5:5) for 16 h. The solvents were removed under vacuo to
provide a pale yellow oil which was compared with an authentic sample prepared
earlier.
$vnthesis of MOM-protected binhenvl resin-bound aryl silane intermediate l2-
Scheme 20)
2-Scheme 20 was prepared in an analogous manner as of compound 2-Scheme 19.
Characteristic peaks in the 1 HNMR (MAS): d 5.0 (s) 2H), 3.4 (s, 3 H)) 0.6 (s,
2H),
0.2 (s, 6 H).
Svnthe5is of 2-hydroxybinhenvl linked silane (3-Scheme 20)
To the MOM protected biphenyl resin-bound aryl silane intermediate (2-Scheme
20,
100 mg) was added 10~lo trifluoroacetic acid in dichloromethane and the
reaction
mixture was agitated by bubbling Argon through the solution for 8 h. The resin
was
filtered, washed with dichloromethane. 1 HNMR (MAS) analysis indicated the
complete disappearance of MOM group. ( 100 mg).
It will be clear to the skilled artisan that the silicon linkers and silicon
based
polymer resins of this invention may be used in a variety of combinatorial
methods
for synthesizing a large number of molecularly diverse compounds,
simultaneously.
For example, the instant invention may be applied to (i) the "multi-pin"
method
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CA 02269737 1999-04-23
WO 98l17695 PCTlUS97/19450
described in Geysen et al., Proc. Natl. Acad. Sci. USA., 81, p. 3998 (1984);
U.S.
Patent 4,708,871 (1987); Geysen et al., Bioorg. Med. Chem. Lett.) 3, p.397
(1993);
and European Patent 138,855 ( 1991 }; (ii} the "tea-bag" approach described in
Houghten, R.A., Proc. Natl. Acad. Sci. USA., 82, p. 5131 (1985); and Houghten
et
al., Nature, 354, p. 84 ( 1991 ); and (iii) chemical synthesis on a "chip"
described in
Fodor et al., Science, 251, p. 767 ( 1991 ) and U. S . Patent 5,143, 854 (
1992}.
In addition, the compounds may be screened in assays which have been
developed for determining Iead compounds as pharmaceutical agents. For reasons
of efficiency, the components of the library are screened in groups of
multiple
compounds. Therefore, once the library of compounds has been synthesized)
there
must be some method to deconvolute the results of screening such that
individual
active compounds can be identified. Based upon the disclosure herein, it will
be
clear to the skilled artisan that there are many methods for deconvolution of
the
combinatorial library. For example) if the compounds of the library are
screened on
a solid support, they may be physically segregated so that individual active
compounds may be directly selected and identified. In contrast, if the
compounds of
the library are cleaved from the resin and tested as soluble mixtures, the
library may
be deconvoluted in an iterative approach, which involves resynthesis of
mixtures of
decreasing complexity until a single compound is identified) or in a scanning
approach) in which the various substituents on the aromatic carbocycle, are
evaluated independently and the structure of active compounds are determined
deductively. For an explanation of the iterative and scanning approaches to
deconvolution of a combinatorial library of compounds, see, for example,
Houghten
et al., Nature, 354, p. 84 (l991).
Biological Assavs:
(I) A representative binding assay is as follows. Other binding assays or
functional assays that are known by, or that would be obvious to the skilled
artisan,
may be performed as well. Tissue containing the appropriate target receptor
are
homogenized, filtered through cheesecloth and centrifuged at 1500 x g for 10
minutes. The supernatant is decanted and the pellet is resuspended in an
appropriate
incubation buffer, e.g. 75 mM Tris~HCl, pH 7.4 containing 12.5 mM MgCl2 and
1.5
mM EDTA. Membranes equivalent to 100 g protein are incubated with 50 pmol
radiolabeled receptor Iigand and an appropriate amount of the test library
mixture in
a total volume of 5001 for 1 hr. at 37~C. The binding reaction is terminated
by
dilution with the addition of 5 mL of cold incubation buffer and the bound
tracer is
separated from free by filtration on Whatman GF/C filter paper. The filter
paper is
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WO 98117b95 PCTlUS97/19450
washed several times with cold incubation buffer and then counted to determine
the
amount of bound Iigand.
Specific binding is defined as the portion of radiolabeled receptor ligand
binding which can be completed by a high concentration of unlabeled receptor
ligand. The presence of a competing ligand in the library test mixture is
evidenced
by a reduction in specific binding of the radiolabeled receptor Iigand in the
presence
of the library test mixture.
{II) An additional assay that is effective and extremely useful for testing
the
aromatic carbocycles prepared according to this invention is disclosed by
Lerner et
al., Proc. Natl. Acad. Sci. U.S.A., 91(5), pp. 1614-1618 (1994), which is
incorporated by reference herein.
The above description fully discloses the invention including preferred
embodiments thereof. Modifications and improvements of the embodiments
specifically disclosed herein are within the scope of the following claims.
Without
further elaboration it is believed that one skilled in the art can, using the
preceding
description, utilize the present invention to its fullest extent. Therefore
any
examples are to be construed as merely illustrative and not a limitation on
the scope
of the present invention in any way. The embodiments of the invention in which
an
exclusive property or privilege is claimed are defined as follows.
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