2,4-DIOXO-PYRIDO[2,3-D]PYRIMIDINE-3-ACETIC ACIDS AND ESTERS AND SALTS THEREOF

ACIDES DE 2,4-DIOXO-PYRIDO[2,3-D]PYRIMIDINE-3-ACETIQUE, LEURS ESTERS ET LEURS SELS

English Abstract

2100164 9212979 PCTABS00014
A series of novel 2,4-dioxo-pyrido 2,3-d pyrimidine-3-acetic
acids and their esters and pharmaceutically acceptable base addition
salts are disclosed. These compounds are useful in therapy as
aldose reductase inhibitors for the control of certain chronic
diabetic complications. Methods for preparing these compounds from
known starting materials are provided.

Claims

-19-
CLAIMS
1. A compound of the formula:
<IMG> I
wherein X is hydrogen, fluorine, chlorine, bromine,
trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 alkylthio;
Q is a divalent alkylene radical having from one to
three carbon atoms; and
R1 is phenyl, thiazolophenyl, trifluoromethyl-
thiazolophenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl, phenyloxadiazolyl, thiazolopyridinyl,
oxazolopyridinyl, imidazopyridinyl, triazolopyridinyl or
indolyl, wherein said phenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl and phenyloxadiazolyl groups are each
optionally substituted with up to two identical or non-
identical substituents on the benzene ring, said identical
substituents being selected from fluorine, chlorine,
bromine, trifluoromethyl, C1-C4 alkyl and C1-C4 alkoxy and
said non-identical substituents being selected from
fluorine, chlorine, bromine, trifluoromethyl, methyl and
methoxy;
R2 is hydrogen; and the pharmaceutically acceptable base
addition salts thereof.
2. A compound as claimed in claim 1 which is an acid
wherein R1 is phenyl or benzothiazol-2-yl, or a ring-
substituted derivative of phenyl or benzothiazol-2-yl.
3. A compound as claimed in claim 2 wherein X is
hydrogen, Q is methylene and R1 is unsubstituted
benzothiazol-2-yl.
4. A compound as claimed in claim 2 wherein X is
hydrogen, Q is methylene and R1 is ring-substituted
benzothiazol-2-yl.

5. A compound as claimed in claim 2 wherein X is hydrogen,
Q is methylene and R1 is ring-substituted phenyl.
6. A compound as claimed in claim 5 wherein R1 is 4-bromo-
2-fluorophenyl.
7. A compound as claimed in claim 5 wherein R1 is 3,4-
dichlorophenyl.
8. A compound as claimed in claim 2 wherein X is chlorine
Q is methylene and R1 is ring-substituted phenyl.
9. A compound as claimed in claim 8 wherein X is chlorine
at the 6-position of the molecule and R1 is 4-bromo-2-
fluorophenyl.
10. A compound as claimed in claim 1 wherein R2 is C1-C6
alkyl.
11. A compound as claimed in claim 10 wherein R2 is ethyl.
12. A compound according to claim 1, which is selected from
the group consisting of:
1-(4-Bromo-2-fluorophenylmethyl)-1,4-dihydro-2,4-dioxo-
3(2H)-pyrido[2 3-d]pyrimidineacetic acid;
1-(4-Bromo-2-fluorophenylmethyl)-6-chloro-1,4-dihydro-
2 4-dioxo-3(2H)-pyrido[2,3-d]pyrimidineacetic acid; and
1-(3,4-Dichlorophenylmethyl)-1,4-dihydro-2,4-dioxo-

20a
3(2H)-pyrido[2,3-d]pyrimidineacetic acid.
13. A pharmaceutical composition for preventing or
alleviating chronic diabetic complications in a diabetic subject,
which composition comprises (a) an amount of a compound as claimed
in any one of claims 1 to 12 effective to prevent or alleviate
such complications and (b) a pharmaceutically-acceptable carrier.
14. A use of a compound as claimed in any one of claims 1 to
12 for treating a diabetic subject to prevent or alleviate chronic
complications arising in the diabetic subject.
15. A compound of the formula:

-21-
<IMG>
wherein X is hydrogen, fluorine, chlorine, bromine,
trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 alkylthio;
and R2 is hydrogen or C1-C6 alkyl; and the pharmaceutically
acceptable base addition salts thereof.
16. A compound of the formula:
<IMG> VI
wherein X is hydrogen, fluorine, chlorine, bromine,
trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 alkylthio;
Q is a divalent alkylene radical having from one to
three carbon atoms; and
R1 is phenyl, thiazolophenyl, trifluoromethyl-
thiazolophenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl, phenyloxadiazolyl, thiazolopyridinyl,
oxazolopyridinyl, imidazopyridinyl, triazolopyridinyl or
indolyl, wherein said phenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl and phenyloxadiazolyl groups are each
optionally substituted with up to two identical or non-
identical substituents on the benzene ring, said identical
substituents being selected from fluorine, chlorine,
bromine, trifluoromethyl, C1-C4 alkyl and C1-C4 alkoxy and
said non-identical substituents being selected from
fluorine, chlorine, bromine, trifluoromethyl, methyl and
methoxy;
R2 is C1-C6 alkyl; and the pharmaceutically acceptable
base addition salts thereof.

-22-
17. A compound of the formula:
<IMG> V
wherein X is hydrogen, fluorine, chlorine, bromine,
trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 alkylthio;
and
R2 is C1-C6 alkyl; and the pharmaceutically acceptable
base addition salts thereof.
18. A process for the preparation of a compound of the
formula:
<IMG> I
wherein X is hydrogen, fluorine, chlorine, bromine,
trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 alkylthio;
Q is a divalent alkylene radical having from one to
three carbon atoms; and
R1 is phenyl, thiazolophenyl, trifluoromethyl-
thiazolophenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl, phenyloxadiazolyl, thiazolopyridinyl,
oxazolopyridinyl, imidazopyridinyl, triazolopyridinyl or
indolyl, wherein said phenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl and phenyloxadiazolyl groups are each
optionally substituted with up to two identical or non-
identical substituents on the benzene ring, said identical
substituents being selected from fluorine, chlorine,
bromine, trifluoromethyl, C1-C4 alkyl and C1-C4 alkoxy and
said non-identical substituents being selected from
fluorine, chlorine, bromine, trifluoromethyl, methyl and
methoxy;

-23-
R2 is hydrogen comprising reacting a compound of the
formula
<IMG> VI
where X, R1 are previously defined and R2 is C1-C6 alkyl,
with an acidic or basic reagent in the presence or absence
of a reaction inert solvent to form a compound of formula I,
and, if desired, converting a compound of the formula I to
a pharmaceutically acceptable salt thereof.
19. A process as claimed in claim 18 wherein R1 is
phenyl or benzothiazol-2-yl, or a ring-substituted
derivative of phenyl or benzothiazol-2-yl.
20. A process as claimed in claim 19 wherein X is
hydrogen, Q is methylene and R1 is unsubstituted
benzothiazol-2-yl.
21. A process as claimed in claim 19 wherein X is
hydrogen, Q is methylene and R1 is ring-substituted
benzothiazol-2-yl or ring-substituted phenyl.
22. A process as claimed in claim 21 wherein R1 is 4-
bromo-2-fluorophenyl or dichlorophenyl.
23. A process as claimed in claim 19 wherein X is
chlorine, Q is methylene and R1 is ring-substituted phenyl.
24. A process as claimed in claim 23 wherein X is
chlorine at the 6-position of the molecule and R1 is 4-bromo-
2-fluorophenyl.
25. A process as claimed in claim 18 wherein R2 is C1-C6
alkyl.
26. A process according to claim 18, said compound
prepared by said process being selected from the group
consisting of:
1-(4-Bromo-2-fluorophenylmethyl)-1,4-dihydro-2,4-dioxo-
3(2H)-pyrido[2,3-d]pyrimidineacetic acid;

-24-
1-(4-Bromo-2-fluorophenylmethyl)-6-chloro-1,4-dihydro-
2,4-dioxo-3(2H)-pyrido[2,3-d]pyrimidineacetic acid; and
1-(3,4-Dichlorophenylmethyl)-1,4-dihydro-2,4-dioxo-
3(2H)-pyrido[2,3-d]pyrimidineacetic acid.
27. A process for the preparation of a compound of the
formula:
<IMG> IV
wherein X is hydrogen, fluorine, chlorine, bromine,
trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 alkylthio;
and R2 is hydrogen or C1-C6 alkyl; comprising condensing a
compound of the formula
<IMG> III
with an ester of isocyano acetic acid in the presence or
absence of a reaction inert solvent, and, if desired
converting the resulting compound to a pharmaceutically
acceptable salt thereof.
28. A process for the preparation of a compound of the
formula:
<IMG> VI
wherein X is hydrogen, fluorine, chlorine, bromine,
trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 alkylthio;

-25-
Q is a divalent alkylene radical having from one to
three carbon atoms; and
R1 is phenyl, thiazolophenyl, trifluoromethyl-
thiazolophenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl, phenyloxadiazolyl, thiazolopyridinyl,
oxazolopyridinyl, imidazopyridinyl, triazolopyridinyl or
indolyl, wherein said phenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl and phenyloxadiazolyl groups are each
optionally substituted with up to two identical or non-
identical substituents on the benzene ring, said identical
substituents being selected from fluorine, chlorine,
bromine, trifluoromethyl, C1-C4 alkyl and C1-C4 alkoxy and
said non-identical substituents being selected from
fluorine, chlorine, bromine, trifluoromethyl, methyl and
methoxy;
R2 is C1-C6 alkyl; comprising alkylating a compound of
the formula
<IMG>
V
wherein X is previously defined and R2 is C1-C6 alkyl,
with an activated aryl alkyl or heteroarylalkyl compound in
the presence of a base condensing agent and a reaction-inert
solvent, and, if desired, converting the resulting compound
to a pharmaceutically acceptable salt thereof.
29. A process for the preparation of a compound of the
formula:

-26-
<IMG> V
wherein X is wherein X is hydrogen, fluorine, chlorine,
bromine, trifluoromethyl, C1-C4 alkyl, C1-C4 alkoxy or C1-C4
alkylthio; and
R2 is C1-C6 alkyl; comprising reacting a compound of the
formula:
<IMG> IV
with a base in alcohol.

Description

~-W092/l2979 21 ~ Q ~ ~ ~ PCT/US91/07943
2,4-DIOXO-PYRIDO~2,3-dlPYRIMIDINE-3-ACET~Ç AC~
; AND ESTERS AND SALTS TH~EOF
This invention relates to 2,4-dioxo-pyrido~2,3-
d]pyrimidine-3-acetic acids, The compounds are useful ~or
the control of certain chronic complications arising from
diabetes mellitus (e.g., diabetic cataracts, retinopathy and
neuropathy`. The present invention also relates to
pharmaceutical compositions comprising such compounds and to
the use of such compounds in treating complications 2risins
from diabetos mellitus.
Past attempts to obtain new and better orai
antidiabetic agents have, ,or the most part, involved an
endeavor to synthesize new compounds that lower blood sugar
levels. More recently, several studies have been conducted
concerning the effect of various organic compounds in
preventing or arresting certain chronic complications of
diabetes, such as diabetic cataracts, neuropathy and
retinopathy, etc. For instance, K. Sestanj et al. in U.S.
Patent No. 3,821,383 disclose that certain aldose reductase
inhibitors like 1,3-dioxo-lH-benz~d,e]isoquinoline-2(3H)-
acetic acid and some closely-related derivatives thereof are
useful for these purposes even though they are not known to
be hypoglycemic. These compounds function by inhibiting the
activity of the enzyme aldose reductase, which is primarily
responsible for catalyzing the reduction of aldoses tlike
glucose and galactose) to the corresponding polyols (such as
sorbitol and galactitol) in the human body. In this way,
unwanted accumulations of galactitol in the lens of
galactosemic subjects and of sorbitol in the lens, retina,
; peripheral nervous system and kidney of diabetic subjects
are prevented or reduced. As a result, these compounds
control certain chronic diabetic complications, including
those of an ocular nature, since it is already known in the
art that the presence of polyols in the lens of the eye
leads to cataract formation and concomitant loss of lens
clarity.

210 !3 1~
Two patent applications to Fujisawa Pharm. K. K., U.S.
Pat 4,734,419 and European Patent Application No. 331,059
~ relate to isomeric 3-substituted 2,4-dioxo-1(2H)-
; quinazolineacetic acids and claim aldose reductase
inhibitory activity and diuretic or antihyperten,ive
; activity, respectively.
1,2,3,4-tetrahydro-2,4-dioxo-3-quinazoline-alkanoic
acids and their use as plant growth regulators, fungicides
and anti-allergenic agents are described by AXademie der
Wissenschaften der DDR in Ger. (East) DD 250,113.
E. Papadopoulous (Journal of Heterocyclic Chemistry,
1981, vol. 15, 515) describes procedures for the preparation
of 2,4-quinazolinedione-3-acetic acids.
Additionally, a series of 3-aryl-2,4-dioxo-1(2H)-
quinazoline acetic acids and derivatives as potential
inhibitors of bovine serum albumin denaturation are
discussed by Bompart, J. et al, Ann. Pharm. Fr., 1988, Vol.
46(6), 361-370; and Montginoul C. et al, Ann. Pharm. Fr.,
1988, Vol. 46(4), pp. 223-232.
Further, 6,8-Dihaloquinazolinon-3-acetic acids are
described by Akademie der Wissenschaften der DDR in Ger.
(East) DD 155,853.
GB 1,401,549 discusses pyrido ~2,3-d~ pyrimidine-
2,4(1H,3H)-diones described as being useful antiinflammatory
agents, analgesics and central nervous system depressants.
Also, Chem. Abstracts, vol. 114, 1991, no. 102035e
discusses thienopyrimidinediones which are described as
aldose reductase inhibitors.
The present invention relates to co~pounds of the
formula
.

~092/12979 2 ~ PCT/US91/07943
Rl is phenyl, thiazolophenyl, tri~luoromethyl-
thiazolophenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl, phenyloxadiazolyl, thiazolopyridinyl,
~- oxazolopyridinyl, imidazopyridinyl, triazolopyridinyl or
indolyl, wherein said phenyl, benzothiophenyl, benzoxazolyl,
benzothiazolyl and phenyloxadiozolyl groups are each
optionally substituted with up to two identical or non-
identical substituents on the bonzene ring, said iden-cical
substituents being selected from fluorine, chlorine,
bromine, trifluoromethyl, Cl-C4 alkyl and C~-C~ alko~y and
said non-identical substituents being selected from
fluorine, chlorine, bromine, trifluoromethyl, ~ethyl 2nd
methoxy;
R~ is hydrogen or C~-C6 alkyl; and the pharmaceutically
acceptable base addition salts thereof.
In a preferred embodiment of the invention, Rl is phenyl
or benzothiazol-2-yl or a ring-substituted derivative of
phenyl or benzothiazol-2-yl. More preferably, Rl is 3,4-
dichlorophenyl or 4-bromo-2-fluorophenyl.
Preferred compounds of the invention are:
l-(4-Bromo-2-fluorophenylmethyl)-l,4-dihydro-2,4-dioxo-
3(2H)-pyrido~2,3-d]pyrimidineacetic acid;
l-(4-Bromo-2-fluorophenylmethyl)-6-chloro-l,4-dihydro-
2,4-dioxo-3(2H)-pyridot2,3-d]pyrimidineacetic acid;
l-(3,4-Dichlorophenylmethyl)-l,4-dihydro-2,4-dioxo-
3(2H)-pyridoE2,3-d]pyrimidineacetic acid.
Specific compounds o~ the present invention include the
following:
l-((6-Chlorobenzothiazol-2-yl)methyl)-l,4-dihy~ro-2,4-
dioxo-3(2H)-pyrido~2,3-d]pyrimidineacetic acid;
l-((6-Fluorobenzothiazol-2-yl)methyl)-l,4-dihydro-2,~-
dioxo-3(2H)-pyrido~2,3-d]pyrimidineacetic acid;
l-((6-(trifluoromethyl)benzothiazol-2-yl)methyl)-1,~-
dihydro-2,4-dioxo-3(2H)-pyrido[2,3-d]pyrimidineacetic acid;

WO92/129~9 2 ~ PCT/US91/07943 _.
6-Fluoro-l-((6-(trifluoromethyl)benzothiazol-2-
yl)methyl)-l,4-dihydro-2,4-dioxo-3(2H)-pyrido[2,3-
d]pyrimidineacetic acid;
-Fluorobenzoxazol-2-yl)methyl)-l,4-dihydro-2,4-
dioxo-3(2H)-pyrido[2,3-d]pyrimidineacetic acid;
l-(2,4-~ichloroph2nylm~thyl)-l,4-dihydro-2,4-dioxo-
3(2H)-pyrido[2,3-d]pyrimidineacetic acid;
6-Chloro-~-(3,4-dichlorophanyl~2thyl)-l,4-dihydro-2,4-
dioxo-3(2~)-pyrido[2,3-d]pyrimidineacetic acid;
I-(3,~-~icnlorophenylmothyl)-l,4-dihydro-6-methoxy-2,4-
dioxo-3(2~j-pyr-do~2,3-d]pyrimidin2acetic acid;
l-(3,4-Dichlorophenvlmethyl)-l,4-dihydro-6-methyl-2,4-
dioxo-3(2~)-pyrido[2,3-d]pyrimidineacetic acid;
l-(4-Bromo-2-fluorophenylmethyl)-6-fluoro-l,4-dihydro-
15 2,4-dioxo-3(2H)-pyrido[2,3-d]pyrimidineacetic acid;
1-(4-Bromo-2-fluorophenylmethyl)-l,4-dihydro-6-methoxy-
2,4-dioxo-3(2H)-pyrido~2,3-d]pyrimidineacetic acid;
l-(4-Bromo-2-fluorophenylmethyl)-l,4-dihydro-6-methyl-
2,4-dioxo-3(2H)-pyrido[2,3-d]pyrimidineacetic acid.
The present invention also relates to a pharmaceutical
composition for the treatment of chronic complications
associated with diabetes comprising a compound of the
formula I or a phar~aceutically acceptable base addition
salt thereof in an amount effective to prevent or alleviate
such chronic complications and a pharmaceutically acceptable
carrier. Specific and preferred compositions of the present
invention comprise the foregoing specific and preferred
compounds.
The present invention also relates to a method for
treating a diabetic subject to prevent or alleviate chronic
complications arising in said subject, which comprises
administering to said diabetic subject an amount of a
compound of the formula I or a pharmaceutically acceptable
base addition salt thereof effective to prevent or alleviate
such complications.
`
' .
.
' ' ~`, ' `
` ~

-~0 92/1297~ 2 ~ ~ ~ J~ PCr/US91/07943
The present invention also xelates to compounds o~ the
following formulae IV, V and VI:
.
:
~ ~ H 11 e C 2 R ~ X--$ ~ b C 2 ~ 2
.,. O
, !~ v
( ~here l n R2 I s C1-C6 ~I ky l )
'
and
o
x~\co2~2
~Rl
V1
(~herein R2 is Cl-C6 al kyl )
which are alkyl 5-halo-2-(3-alkoxycarbonylmethylureido)
pyridine-3-carboxylates, alkyl l,4-dihydro-2,4-dioxo-3~2H)-
pyrido[2,3-d]pyrimidine acetates, and alkyl l-(substituted
benzyl) 1, 4-dihydro-2, 4-dioxo-3 (2~I) -pyrido~2, 3-
30 d]pyrimidineacetates, respectively, wherein X, Q, Rl and R2
are as defined above. These compounds are useful as
intermediates for preparing the compounds of
the formula I.
.~ The following reaction scheme illustrates the
35 preparation of the compounds of the present invention.
.
.
.

WO 92/12979 2 1 ~, ?\, 1 & '-~ Pcr/US9l/07943 ,-.
--6--
i
~\ N H 2 ~ C O, C H ~,
II III
. .
rc cl.2co222 ~\r~\co2~a
(whereln R2 15 Cl-C6 alkyl)
lV V
~[~ CO2R2 ~ ô
( where I n R2=C1-C6 al ky 1 ) ( where 1 n R2=H )
V I
~-In accordance with the process employed for preparing
:the compounds of the present invention, an appropriately
substituted carboxylic acid ester of formula VI is converted
`, ~ ', ': ,: ,

-W092/12979 2 1 v 9 ~ s PCT/US9l/0794
-7-
by means of a suitable reagent or reagents into the title
compounds of formula I. Such reagents wh,ich may be useful
for this transformation are those which are often employed
by those skilled in the art for converting carboxylic acid
esters to the corresponding carboxylic acids and may
include sodium or potassium hydroxides, hydrochloric acid,
trifluoroacetic acid and the like. These reagents may be
used in the presence or absence of a reaction-in2.. solvent
such as water, lower alcohol, lower ether or cyclic ether,
or an organic acid (such as acPtic acid). A solution of
sodium hydro~ide in wa.er is preferred for tnis step.
Furthermore, these reactions may be carried out at a
temperature that is in the range of aboul 0C up to the
boiling point of the solvent employed, and is preferably
conducted in the range of about 20C to about 40C.
Isolation of the desired products of formula I may be
effected by adjusting the pH of the reaction mixture to
within the range of about 1 to about 7, followed by
filtration of the precipitated acidic product I or by
extraction of the crude product into a water-immiscible
solvent which may be subsequently dried and evaporated to
obtain product acid I. Further purification may then be
accomplished by crystallization/recrystallization of the
crude product I from a suitable solvent system or by
chromatographic methods.
The appropriately substituted carboxylic acid esters of
formula VI ~in which Q Rl and R2 are as previously defined),
the immediate precursors to the title co~pounds of formula
I, are themselves all novel compounds and are readily
prepared by the N-alkylation of the N-l unsubstituted
compounds of formula V by analogy with methods reported in
the scientific literature and familiar to those skilled in
,^ the art. Thus, the intermediates of formula V, which
possess a removable hydrogen atom at the 1-position of the
pyrido~2,3-d~pyrimidineacetate may be alkylated with a
variety of activated arylalkyl or heteroarylalkyl compounds
,' ,
.
.
.~

WO9 /12979 ~ ` PCT/US91/07943 ~
2 1 ,, O l ~ !_
of general formula Z-Q-RI, where Q and Rl are as previously
defined and Z is a leaving group such as halogen or lower
alkane-sulfonate. This particular reaction is normally
carried out in tbe presence of a base condensing agent, such
as an alkali metal hydride, alkanoate or amide, or an alkali
metal-alkyl or metal-aryl compound, as the case may be.
Furthermore, the reaction is usually conducted in a
rPaction-inert organic solvent, preferably using ~,N-di-
(lower al~yl) lower alXanoamide for the best results;
preferred agents in this connection would include sodium
hydride as the bas2 condensing agent and N,N-
dimethylformamide as the solvent. In general,
substantially eauimolar quantities of the reactants are
employed. The preferred temperature range is from about oc
up to about the boiling point of the solvent employed for a
period of about O.5 hours to about 48 hours. In practice,
the reaction is usually conducted at room temperature for a
period of time which is often less than 24 hours. In
addition, while this reaction may be conducted at pressures
up to 5 atmospheres, in practice it is adequate to perform
this step at atmospheric pressure, usually under an inert
atmosphere such as nitrogen or argon gas and with suitable
exclusion of moisture which could decrease the yield of
intermediate product VI. Upon completion of the reaction,
as determined using any of a variety of methods (such as
thin layer chromatography), the desired N-l substituted
esters of formula VI are recovered from the reaction mixture
by the use of any number of standard tec~niques known to
those skilled in the art. In practice, the reaction mixture
is first diluted with water and the crude reaction product
is then filtered (in the case of a precipitated solid
product) or extracted into a suitable, water-immiscible
solvent from which the crude intermediate of formula VI may
be isolated by evaporation of the solvent to dryness.
Further purification of these compounds may best be
accomplished as in the case of the final acid products of
.
~ .

. W O 92/12979 ~ PC~r/US91/07943
_g_
formula I, i.e., by crystallization /recrystallization from
a sultable solvent system, or by chromatography of the crude
reaction product.
Finall~, the N-1 unsubstituted esters of formula V are
themselves novel compounds and they may be prepared by one
of several methods reported in the scientific literature.
For examF'e, E. Papadopoulos (Journal of Heterocyclic
Chemistry, 1981, vol. 18, 515) has described a procedure for
the convPrsion of a ureido ester into a 2,4-
quinazolinedio..~-3-ac2tic acid by treating the former with
concent.at_d a~2onium hydroxide in ethanol at 25C. In the
examples desc ibed within the present invention, the novel
ureido esters of formula IV are similarly best converted to
the compounds of formula V by the action of concentrated
lS ammonium hydroxide in ethanol at 50C. The same ureido
esters of formula IV are prepared by the condensation of the
appropriate methyl nicotinate III with an ester of
isocyanoacetic acid, this condensation taking place with
equimolar amounts of the two components in the presence or
absence of a reaction-inert solvent. In all cases, the
compounds of formula III, the starting materials for the
preparation of the uraido esters of formula IV are either
commercially available or are readily prepared using methods
and procedures found in the scientific literature.
Esters of the general structural type VI may be
~; isolated prior to conversion to the acids of structure I.
In instances when a different ester is desired, the acid I
may be esterified using any variety of procedures known to
those skilled in the art of organic chemistry. For example,
the acid I may be suspended in the appropriate C~-C6 alcohol
and treated with a suitable inorganic acid (e.g.,
. hydrochloric acid or sulfuric acid) and then stirred under
an inert atmosphere with the exclusion of moisture at a
temperature within the range of room temperature to about
the boiling point of the alcohol employed. The crude ester
VI so obtained may be isolated by removal of the solvent

W092/12979 2 ~ ~V Q3~ PCT/US91/0794~ ~
--10--
alcohol and purification by recrystallization,
chromatography, distillation or other suitable technique.
The chemical bases which are used in this invention to
prepare the aforementioned pharmaceuticall~ acceptable bas2
addition salts are those which form non-toxic base salts
with the herein described 1-substitu~2d 2,4-dio~o-
pyrido[2,3-d]pyrimidine-3-acetic acids, such as 1-(4-bromo-
2-flurophenylmethyl)-6-chloro-1,4-dihydro-2,4-dioxo-3(2~)-
pyrido[2,3-d]pyrimidineacetic acid. These part-cul2r r.~n-
toxic base salts include thos2 d6,iv-d f,ro~ ~uc.
pharmacologically acceptable cations as sod um, ~o~assium,
calcium, magnPsium~ etc. These salts can be easily preparPd
by treating the aforementioned acid compounds with an
aqueous solution of the pharmacologically acceptable cation
and then evaporating the resulting solution to dryness,
preferably under reduced pressure. Alternatively, they may
also be prepared by mixing lower alXanolic solutions of the
acidic compounds and the desired alkali metal alkoxide
together, and then evaporating the resulting solution to
dryness in the same manner as above. In either case,
stoichiometric quantities of the reagents must be employed
to ensure completeness of the reaction and maximum
production of yields of the desired final base addition
salts.
Also, salts of the title compounds may be prepared
using pharmacologically acceptable organic basas to form the
salts, these organic bases including compounds such as
diethanolamine, meglumine, cyclohexylamine, dicyclo-
hexylamine and the like. The salts derived from these
organic bases may be prepared by combining the two reagents
in essentially equimolar amounts in a suitable solvent from
which the derived base addition salt can be isolated by
virtue of its reduced solubility in the solvent system, or
by concentration of the solvent system to dryness followed
by crystallization/recrystallization of the crude salt in a
suitable solvent system.

~092/12979 2 ~ 3ix P~T/US91/07943
--11--
The starting materials required for preparing the
compounds of formula I are either known compounds which are
readily available commercially or they are described in the
literature or else they can easily be synthesized by those
skilled in the art starting from common chemical reagents
and using conventional methods of organic synthesis. For
instance, 2-aminonicotinic acid is readily prepared from th~
known 2-aminonicotinonitrile (Beilstein, 22, 5~2).
The compounds of the formula I and the pharmaceutically
acceptable salts thereof (hereinafter also referred to as
the active compounds of the present invention) are readily
adapted to therapeutic use as aldose reduc~a e inhibito-s
for the control of certain chronic diabPtic complicatio~s,
in view of their ability to reduce lens and peripheral nerve
(e.g., the sciatic nerve) sorbitol levels in diabetic
subjects. The active compounds of the present invention can
be administered to affected mammals (including humans) by
either the oral, topical or parenteral routes of
administration. In general, these compounds are ordinarily
administered in dosages ranging from about 0.50 mg to about
50 mg per kg of body weight per day, although variations
will necessarily occur depending upon the weight and
condition of the subject being treated and the particular
route of administration chosen.
These compounds may be administered either alone or in
combination with pharmaceutically acceptable carriers by the
various routes previously indicated, and such administration
:
can be carried out in either single or multiple dosages.
More particularly, the active compounds of this invention
can be administered in a wide variety of different dosage
forms, i.e., they may be combined with various
pharmaceutically-acceptable inert carriers in the form of
tablets, capsules, lozenges, troches, hard candies, powders,
sprays, aqueous suspensions, injectable solutions, elixirs,
syrups, and the like. Such carriers include solid diluents
or fillers, sterile aqueous media and various non-toxic
,:, ' ..

W09~/~t9~9 21i?"3.~'~ PCI/U591/07943 ~`
--12--
organlc solvents. In general, the active compounds of the
invention will be present in such dosage forms at
concentration levels ranging from about 0.5% to about 90~ by
weight of the total composition to provide the desired unit
dosage.
For oral administration, tablets containing various
excipients such as sodium citrate, calcium carbonate and
calcium p~.osphate may b2 employed along with various
disintegrants such as starch and preferably potato or
tapioca starch, alginic acid and certain complex silicates,
together with binding agents such as polyvinylpyrrolidone,
gelatin and acacia. Additionally, lubricating agents such
as magnesium stearato, sodium lauryl sulfate and talc are
often very useful for tabletting purposes. Solid
compositions of a similar type may also be employed as
fillers in soft and hard-filled gelatin capsules; preferred
materials in this connection also include the high molecular
weight polyethylene glycols. When aqueous suspensions
and/or elixirs are desired for oral administration, the
essential active ingredient therein may be combined with
various sweetening or flavoring agents, coloring matter or
dyes, and if so desirPd, emulsifying and/or suspending
agents as well, together with such diluents as water,
ethanol, propylene glycol, glycerin and various combinations
thereof.
For parenteral administration, solutions of the active
compounds of the present invention may be prepared, taking
into account the solubility of the compound or salt to be
utilized. Thus, solutions in sesame or peanut oil or in
aqueous propylene glycol or N,N-dimethylformamide as well as
sterile aqueous solutions may be employed. Such aqueous
solutions should be suitably buffered if necessary and the
liquid diluent first rendered isotonic with sufficient
saline or glucose. These particular aqueous solutions are
especially suitable for intravenous, intramuscular,
subcutaneous and intraperitoneal injection. In this
., . . ., . ~ , , .
,
~, ..

~V092/12979 2 1 a ~ PCT/US91/n7943
-13-
connection, the sterile aqueous media employed are all
readily obtainable by standard techniques well-known to
those skilled in the art. Additionally, it is also possible
to administer the compounds topically via an appropriate
ophthalmic solution (e.g., 0.5-2.0%) applied dropwise to the
eye.
The L'ility of the compounds of the present invention,
as agPn.s for th~ control of chronic diabetic complications,
may be predicted by measuring their ability to (1) inhibit
the enzyme activity of isolated aldose reductase; (2) reduce
or inhibit sorbitol accumulation in the sciatic nerve and
lens of acutely streptozotocinized (i.e. diabetic) rats; (3)
reverse 21rsady-elevated sorbitol levels in the sciatic
nerve and/or lens of chronic streptozotocin-induced diabetic
rats; (4) prevent or inhibit galactitol formation in the
lens of acutely galactosemic rats, and/or (5) delay cataract
formation and reduce the severity of lens opacities in
chronic galactosemic rats.
The following Examples illustrate the preparation of
the compounds of the present invention. All melting points
are uncorrected. Ratios of solvents used in thin layer
chromatography (TLC) are by volume.
Example l
Ethyl 1-(4-bromo-2-fluorophenylmeth~L-6-chloro-1.4-dihydro-
2.4-dioxo-3(2H-~yrido[2.3-d]py~ eacetate
; A. 2-Amino-5-chloro-nicotinic acid
A mixture of 10 g (72 mmol) of 2-aminonicotinic acid in
300 ml acetic acid was treated with chlorine gas for 1 hour
at room temperature. During this time, the solution
initially became homogeneous and then a yellow product
precipitated. The reaction mixture was then poured into
1000 ml of ethyl ether, stirred for one half hour and then
filtered. The solids were washed with ethyl ether and then
dried to give 12.46 g (99%) of the title compound, m.p. 250-
255C.
. -:.
. , ' ' .

W092/12979 2 ~ PCT/US91/07943
-14-
B. Methyl 2-amino-5-chloronicotinate
A mixture of 6.2 g (36 mmol) of the title compound of
Example lA and 70 ml methanol was treatPd with HCl gas for
2 hours, refluxed for 16 hours (a ho~ogcn2Gus solution
resulted) and then treated with HCl gas for an additional 2
hours. TLC (90 C~Cl3:10 metnanol) h~n shc~od c~mplotion o~
reaction (RF 0.70 vs 0.10 for th~ title co~pound of Example
lA). The solvent was removed in '12CUO, rho sol l ds wo~~
washed with 5~ NaHCO3, and then wi-h wa~2;^, and ~2re tnen
dried overnight under vacuum ~c yl~ld rn~ ~ tlo comnound~
6.21 g (93%), m.p. 260-263C, m/~ 5 (p+), 188.
Similarly, 5.0 g (36 mmol) 2-aminonicotinic acid
(Aldrich Chemical co.) in so ml methanol was converted to
5.4 g (98%) methyl 2-aminonicotinate, m.p. 82-a40c.
c. Ethyl 6-chloro-1 4-dihvdro-2.4-dioxo-3(2H)-~yrido-
r 2l3-d]~vrim~di~eacetate
A mixture of 6.21 g (33 mmol) of the title compound of
Example lB and 3.73 ml of (33 mmol) of ethyl
isocyanatoacetate was heated until the mixture became
homogeneous and heating was then continued for an additional
15 minutes. On cooling, the material became a hard, gummy
solid which was then dissolved in 50 ml of absolute ethanol,
treated with 20 ml concentrated NH40H and stirred 3 hours at
50C. TLC (1 ethyl acetate:l hexane) showed conversion to
a product (at Rf 0.60). The solution was cooled, excess
ethanol was removed ~n vacuo and the aqueous residue was
acidified with about 100 ml of lN HC1. The resulting
yellow-orange solid was filtered, washed with lN HCl and
dried to give 7.2 g crude product. Recrystallization from
ethanol gave 2.33 g (25%) of the title compound, m.p. 112-
114C; m/e 283 (p+), 285; Analysis for CIlHloO~Cl: Calc~d: C
46.57; H 3.55; N 14.81; Found: C 46.21, H 3.51; N 14.85.
Similarly, 5 g methyl 2-aminonicotinate and 4.66 ml
ethyl isocyanatoacetate gave, after treatment with 60 ml
ethanol and 20 ml concentrated NH40H at 50C for 1 hour,
acidification to pH3, extraction with ethyl acetate (2xlOO
.

-~092/12979 ~ 1 9r~, ~3 !'~ PCT/US91/n7943
-15-
ml) and concentration of the organic extracts, 6 21 g of
crude product. Recrystallization from ethanol gave 3.2 g
(35.5%) of ethyl 1,4-dihydro-2,4-dioxo-3(2H)-pyrido[2,3-
d]pyrimidineacetate q~arter hydrate, m.p. 109-113C; m/e:
249 (p+); Analysis for CI~HllN304%H2G; Calc~d: C 52.07; H 4.57;
N 16.56; Found: C 52.15; H 4.43; N 16.62.
D. EthYl 1-(4-bromo-2-fluorophenylmethyl)-6-chloro-
1 4-dihydro-2 4-dioxo-3(2HL-~yridoL2 3-dlpv_imid~n2aceta~
Under N. in a flame dried flask with magnetic stirrer,
0.310 g (7.8 mmol) of NaH (60% in oil disp~rsion) was w2shGd
with pentane. The resulting oil free solid was suspended in
35 ml of sievP-dried N,N-dinethyl~or~a~idG (~:F~ a-.~ 2.00
g (7.1 mmol) of the title compound or ~xampie lC was added
portionwise with stirring. After H2 evolution had ceased
(about 0.5 hour), 4-bromo-2-fluorobenzyl bromide (1.89 g,
7.1 mmol) was added in one portion. After 2 hours, a thick
suspension had formed, and an additional 10 ml DMF was
added. After an additional 16 hours at room temperature,
TLC (75 hexane: 25 ethyl acetate) showed product (RF 0.80)
` 20 and no starting material (RF 0.30). The reaction mixture
was poured over 200 ml ice/H2O, stirred 30 minutes, filtered,
washed well with H~O and then air dried to give 3.12 g crude
product. Recrystallization from ethanol gave the title
compound as a pure product, 2.85 g (86.1%), m.p. 145-147C.;
m/e: 469 (p+), 471.
Similarly, 3.0 g (12 mmol) ethyl 1,4-dihydro-2,4-dioxo-
3(2H)-pyrido~2,3-d]pyrimidineacetate, 0.529 g (13.2 mmol)
60% NaH and 3.22 g (12.0 mmol) 4-bromo-2-fluorobenzyl
bromide in 50 ml dry DMF gave 2.65 g (50.5%) ethyl 1-(4-
bromo-2-fluorophenylmethyl)-1,4-dihydro-2,4-dioxo-3(2H)-
pyrido~2,3-d]pyrimidineacetate, m.p. 140-143C.
Similarly, 1.74 g (7.0 mmol) ethyl 1,4-dihydro-2,4-
dioxo-3(2H)-pyrido~2,3-d]pyrimidineacetate and 1.36 ml (7.0
mmol) alpha,3,4-trichlorotoluene (97%, Aldrich Chemical Co.)
gave 2.61 g (91%) ethyl 1-(3,4-dichlorophenylmethyl)-2,4-
dioxo-3(2H)-pyrido~2,3-d]pyrimidineacetate, m.p. 136-138C.

WO92~12979 21 ~ v ~ PCT/~S91/07943
-16-
Example 2
1-(4-Bromo-2-fluorophenylmethy11-6-chlo~o-ll4~ ihYdro-2~-
dioxo-3(2H~-~vrido[2 3-d~PYrimL~inÇYL~o~ gi~
A mix.ur~ oP 1.40 g (2.97 mmol) of the title compound
of Example lD, 15 ml concentrated HCl and 50 ml glacial
acetic acid was refluxed for 16 hours. T~C (75 hexane:25
ethyl acetate) showed only a single spot at Rf 0.10. After
concentration ln vacuo, the residue was recrystallized from
ethyl acetate:hexane (120:55 ml) to give the title compound
as yellc~ c_ystals, 0.728 g (55.3%), m.p. 195-197C;
Analysis for C~jH~rCl~N3O~, Calc~d: c 43.42; H 2.28; N 9.49;
Found: c ~3.~; H 2.34; N 9.35.
Example 3
1-(4-Bromo-2-fluoroDhenylmethyl)-1.4-dihydro-2,4-dioxo-3(2H-
~vridor2.3-dlpvrimidineacetic acid hydrochloride
A mixture of 2.30 g (5.27 ~mole) ethyl 1-(4-bromo-2-
fluorophenylmethyl)-1,4-dihydro-2,4-dioxo-3(2H)-pyrido[2,3-
d]pyrimidineacetate and 50 ml 2N NaOH in 100 ml absolute
ethanol was stirred for 3 hours at room temperature,
resulting in a homogeneous solution. The solution was
acidified to pH 7 and extracted with ethyl acetate (2x100
ml). The organics were washed with water, dried over Na~SO4
and concentrated ln vacuo to a viscous oil. Trituration
with hexanes gave 1.3 g of crude product, recrystalized from
methanol to give the title compound, 0.60 g t26S), as the
hydrochloride salt, m.p. >300C; Analysis for
C~HI~BrFN~O~-HCl: Calc'd: C 43.22; H 2.72; N 9.45; Found: C
43.60; H 2.33; N 9.10.
Similarly, 2.4 g (5.87 mmole) of ethyl 1-(3,4-dichloro-
phenylmethyl)-2,4-dioxo-3(2H)-pyrido~2,3-d]pyrimidineacetate
in 90 ml ethanol with 20 ml 2N NaOH gava 0.370 a (17%) 1-
(3,4-dichlorophenylmethyl)-1,4-dihydro-2,4-dioxo-3(2H)-
pyrido[2,3-d]pyrimidineacetic acid as white crystals from
ethyl acetate:hexane), m.p. 205-208OC; m/e 379 (pr)~ 381;
Analysis for Cl6HlICl~N3O~: Calc'd: C 50.55; H 2.92; N 11.05;
Found: C 50.54; H 2.75; N 10.84.
. .
.. . .
.-.

WO~2/12979 2 ~ ~ 9 ~ ~ ~ PCT/US91/07943
-17-
Example 4
The compounds of Examples 2 and 3 were tested for their
ability to reduce or inhibit aldose reductase enzyme
activity via the procedure of S. Hayman et al., as described
in the Journal of Biological Chemistry, Vol. 240, p.877
(1965) and as modified by K. Sestanj et al. in U.S. Patent
No. 3,821,383. In each case, the substrate employed was
partially purified aldose reductase enzyme obtained from
human placenta. At a concentration of lO~m the compounds
showed a percent inhibition greater than 70%.
Example 5
The compounds of Examples 2 and 3 were tested for their
~; ability to reduce or inhibit sorbitol accumulation in the
sciatic nerve and lens of streptozotocinized (i.e.,
diabetic) rats by the procedure described in U.S. Patent No.
3,821,383. In the present study, the amount of sorbitol
-; accumulation in the sciatic nerve and lens of each test
;:~ animal was measured 27 hours after the induction of
diabetes. The compounds were the administered orally at 25
mg/kg at intervals of 4, 8 and 24 hours after the
administration of streptozotocin. The results obtained in
this manner are presented in terms of the percent inhibition
(%) afforded by the test compound as compared to the case
where no compound was administered (i.e., the control or
untreated animal where sorbitol levels normally rise from
approximately 50-lO0 nM/g tissue to as high as 400 nm/g
tissue in the 27-hour test period). In this manner, it was
found that each compound afforded a reduction in the
accumulated sorbitol levels in the sciatic nerve of diabetic
rats of at least 60~ and a reduction in the lens of at least
4%.
'
i