Note: Descriptions are shown in the official language in which they were submitted.
~844~
~ACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to chemical compounds
of the peptide type produced by synthetic methods and
includes various processes.
2. Description of the Prior Art
Bestatin is a chemical active as an inhibitor
of certain enzymes which was originally produced by ~er-
me~tation of Streptomyces olivoreticuli as disclosed in
various patents (see Farmdoc 09548X) and the following
publications:
1. Umezawa, H.; T. Aoyagi, H. Suda, M. Hamada &
T. Takeuchi: Bestatin an Inhibitor of Aminopeptidase
B, Produced by Actinomycetes. J. Antibiotics 29:97-99,
1976.
2. Suda, H.; T. Takita, T. Aoyagi & H. Umezawa:
The Structure of Bestatin. J. Antibiotics 29:100-101,
1976.
3. Nakamura, H.; H. Suda, T. Takita, T. Aoyagi,
H. Umezawa & Y Iitaka: X-Ray Structure Determlnation
of (2S,3R)-3-amino-2-h~droxy-4-phenylbutanoic Acid, a
New Amino Acid Component of Bestatin. J. Antibiotics
29:lG2-103, 1976.
4. Suda, H.; T. Takita, T. Aoyagi and H. Umezawa:
The Chemical Synthesis of Bestatin. J. Antibiotics
2 :600-601, 1976.
5. Umezawa, H.; M. Ishizuka, T. Aoyagi and T. Takeuchi,
Enhancement of Delayed-Type Hypersensitivity by Bestatin, an
Inhibitor of Aminopeptidase B and Leucine Aminopeptidase, J.
Antibiotics 29, 857-859, 1976.
Bestatin has the chemical name [(2S,3R)-3-amino-2~
hydroxy-4-phenylbutanoyl[-L-leucine and the following structure
-2- ~
CH2-~_C-CO--NH--C-COOH
H OH fH2
CH
H3C CH3
SU~MARY OF THE INVENTION
According to the present invention, there is provided a
compound represented by the following formula (I):
1 3 2 1 2' 1'
R -- CH - jH - CO - NH -- CH - COOH ( I )
NH 2 OH R
where Rl is hydroxybenzyl and R2 is a member selected from the
group consisting of alkyl having 1 to 6 carbon atoms, hydroxy-
alkyl, mercaptoalkyl, carboxamidoalkyl, alkoxyalkyl, alkyl-
mercaptoalkyl, carboxyalkyl, aryl, aralkyl and substituted
aralkyl.
Bestatin is (2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl-
(S)-leucine which is a compound represented by said Formula (I)
wherein Rl is benzyl and R2 is isobutyl.
~.~
11 1 8 4~
A preferred embodiment of the present invention
is a compound having the formula
l 3 2 l 2' l'
R -CH -CH-CO-NH-IH_COOH
NH2 OH R
wherein R is
nd ~ i8 (lower)alkyl ha~ing 1 to 6 carbon atoms,
hydroxy(lower~alkyl, alkylthioalkyl, carboxamido(lower)-
alkyl, carboxy(lower)alkyl, phenyl or benzyl.
Another pre~erred embod~ent of the present
invention iB a compound ha~lng the formula
3 2 l 2' 1'
Rl-fH--CIH-CO-NH-CIH-COOH
NH2 OH R
~herein Rl i~
OH
~CH2
a n ~ R2 18 (lower)alkyl having 1 to 6 carbon atoms,
hydroxymethyl, methylthioethylJ C~ C~2CO ~ , -C~ C~ COOH,
phenyl or benzyl.
34~1
Another preferred embodiment of the present
invention is a compound naving the formula
3 2 1 2' 1'
Rl-CH -CH~CO NH-CH-COOH
1 2
NH2 OH R
wherein Rl is
and R2 ~ (lower)alkyl ha~lng 1 to 6 car~on atom~ 3
hgdroxymethgl, methylthioethyl, -C ~ C ~ CO ~ , -C~ C~ COOH,
phenyl or ~enzyl.
Another preferred embodiment of the present
lnvention i8 a compound having the formula
1 3 2 1 2' 1'
R -CH -CH-CO-NH-CH-COOH
1 2
NH2 OH R
whereln Rl i~
HO ~ C ~ -
and R2 i~ (lower)alkyl having 1 to 6 carbon a~oms.
Preferred specie~ of the pre~ent invention in-
clude the ~ollowlng:
(2R~3RS)-~-amino-2-hydroxy-4-p-hydroxyphenyl-
butanoyl-(S)-leu~ine.
(2~,3R)-3-amino-2-hydroxy-4-p-hydroxyphenyl-
butanoyl-(5)-leucine.
~,
,,~
``` 111~441
The invention also includes a process for the preparation
of the compounds rePresented by Formula (I) in the following
manner:
A nitrile derivative as represented by a formula (II),
R -CH CH-CN
NH2 OH (II)
(wherein Rl is a group as defined above) or such a nitrile der-
ivative whose amino group is protected is hydrolyzed with an
acid to prepare an amino acid as represented by a formula (III),
Rl -IH - CH-COOH
NH2 OH (III)
(wherein Rl is a group as defined above). After having protected,
if necessary, the functional groups which do not take part in the
reaction, this amino acid and an amino acid represented by the
formula (IV)
NH2 -fH-COOH
R2 (IV)
(wherein R2 is a group as defined above) are condensed in the
ordinary peptide linking method. When said protected groups are
removed, the compounds as represented by Formula (I) are obtained.
There is also provided by the present invention a process
for producing a peptide represented by the formula
1 3 2 1 2' 1'
R -~H CH-CO-NH-CH-COOH
NH2 1H R2
(wherein Rl and R2 are groups as defined above)com~rising con-
secutive steps in which a nitrile represented by the formula
R1 _ ~H I H- CN
NH2 H
(wherein Rl is a group as defined above) or a nitrile derivative
whose amino group is protected is hydrolyzed with an acid to
lllB4'~
repare an amino acid represented by the formula
R _CH--CH_COOH
NH 2 OH
(wherein Rl is a group as defined above); after having pro-
tected, if necessary, the functional groups which do not
participate in the reaction, the resulting amino acid and an
amino acid as represented by the formula
NH 2-CH-COOH
R2
(wherein R2 is a group as defined above) are condensed in an
ordinary pe tide linking process; and then said protecting
group is removed and, preferably, said process wherein R is
p-hydroxybenzyl or su~stituted benzyl and R2 is alkyl or
hydroxymethyl having 3 or 4 carbon atoms and also said process
wherein Rl is p-hydroxybenzyl and R2 is alkyl having 4 carbon
atoms and also said process wherein the acid which is employed
for hydrolysis is hydrochloric acid, hydrobromic acid or
sulfuric acid.
There is also provided by the present invention a
process for collecting an antipode comprising consecutive steps
in which an amino acid represented by the formula
R1 - fH--CH_COOH
NH 2 1H
(wherein R is a group as defined above) is protected by
benzyloxycarbonyl; and said diasteroisomer is selectively
crygtallized in organic solvents in the form of dicyclohexyl-
amine salt.
4~1
mere is further provided bv the present invention a pro-
cess for collecting an antipode comprising consecutive steps in
which an amino acid re~resented by the formula
R -~CH ~ H-COOH
(wherein R is a group as defined above) is protected by benzy-
loxycarbonyl; the thusly protected amino acid is dissolved in an
organic solvent selected from a grou~ of alcohols, ethers,
esters, ketones, halogenated hydrocarbons, dimethylformamide,
dimethylacetamide and acetonitrile; then to the resulting sol-
ution an organic solvent selected from a group of ~etroleum
hydrocarbons, aromatic hydrocarbons, hexane and cyclohexane is
added so as to optically resolve the same and preferably said
process wherein Rl is p-hydroxybenzyl and also said process
wherein the organic solvents are ethyl acetate and petroleum
ether.
There is also provided by the present invention a com~ound
represented by the formula
~; -8-
' ,~.~';;~
R -fH - CH-COOH
NH2 OH
wherein Rl is hydroxybenzyl and particularly is
(2S,3R)-3-amino-2-hydroxy-4-~-hydroxy~henyl-butanoic
acid or
(2RS,3RS)-3-amino-2-hydroxy-4-p-hydroxy~henyl-butanoic
acid.
_ g
Typical examples of nitrile derivatives as represented by
Formula (II~ are 3-amino-2-hydroxy~4-p-hydroxyphenylbutyronitrile
and 3-amino-2-hydroxy-4-o-hydroxyphenylbutronitrile. Any known
amino-protecting group such as those el~Dloyed in peptide chem-
istry may be used for protection of the amino groups. Preferred
exam~les of acyl type amino-~rotecting groups are a formyl group,
an acetyl group, a trifluoroacetyl group, substituted or non
substituted benzoyl group; examples of urethane type amino-
protecting groups are substituted or non-substituted benzyloxy-
carbonyls, alkoxycarbonyl group having 1 to 6 carbon atoms andcycloalkanoxycarbonyl group; preferred examples of other amino-
protecting groups are substituted or non-substituted arylsulfonyl
group, phthalyl group, o-nitrophenylsulphenyl group or trityl
group. Any type of acid usually employed for hydrolyzing
nitriles may be used in the present invention for hydrolysis.
Examples of inorganic acids include hydrochloric acid, hydro-
bromic acid and sulfuric acid; examples of organic acids include
alkylsulfonic acids such as methanesulfonic acid, ethanesulfonic
acid, arylsulfonic acid such as benzenesulfonic acid and toluene-
sulfonic acid. The concentration of these acids may be at anylevel usable for hydrolyzing ordinary nitriles. However, a
concentration of above lN will be preferred.
To the compounds whose amino group is protected
S ~ , 10--
and which are not readily dissolved in the aqueous solution
of acid, an organic solvent which is miscible with water
such as tetrahydrofuran, dioxane, lower alcohols,
acetone, dimethylformamide, dimethylacetamide and dimethyl-
sulfoxide may be added to enhance the solubility of the
compounds in the aqueous solution.
In the case when a protecting group is employed~
if the protecting group is removed during the hydrolysls to
form electrophilic bodies, a cation scavenger such as
anisole may be added. The hydrolytic temperature may be
at any level within the range from room temperature to the
temperature at which reflux of the reaction mixture takes
place. To isolate the desired amino acid from the
reaction mixture, any ordinary method for isolating amino
acid may be applied. For example, when the hydrolysis is
effected with a volatile acid, the exce~sive acid may
be removed by concentrating the reaction rnixture under
reduced pressure and the residue dissolved in water and
neutralized with aqueous alkali solution to the isoelectric
point. Then, if necessary, acetone, methanol or ethanol
i~ added to the reaction mixture to crystallize the in-
tended compound as represented by Formula (III), which is
then separated by filtration. Or otherwise, when a non-
volatile acid is used the reaction mixture is diluted with
water to less than lN acid and allowed to pass through a
strong acidic ion exchange resin so that the desired amino
acid can be adsorbed to the ion exchange resin. The ad-
sorbed amino acid is eluted from the ion exchange resin
with a volatlle alkali such as ammonia water and condensed
under reduced pressure. If necessary acetone, methanol or
ethanol is added to crystallize the intended compound as
~B~
represented byFormula (III)~ which is then se~arated by filtra-
tion.
In the foxegoing reaction, when an (~)-nitrile derivative
is used as a starting material, (2RS,3R)-amino acid is obtained;
when a (S)-nitrile derivative is used, (2RS,3S)-amino acid is
obtained: whenan (RS)-nitrile derivative is used, (2RS,3RS)-
amino acid is obtained.
The comPounds obtained as represented by Formula (III) can
be used as a raw material in the process as described herein-
below. For example, 3-amino-2-hvdroxy-4-p-hydroxyphenylbutanoic
acid (hereinafter, this amino acid is abbreviated as AHPA(p-OH))
i5 in (2S,3R) form. Therefore, in order to obtain this compound,
it is necessary to resolve (2RS,3R)-AHPA(p-OH) to (2S,3R)- and
(2R,3R)-AHPA(p-OH).
(2RS,3R)-AHPA(p-OH) can be resolved optically in ethyl
acetate in the form of diasteroisomer which is obtained by first
benzyloxycarbonylation of (2RS,3R)-AHPA(p-OH) in the ordinary
manner to prepare benzyloxycarbonyl-(2RS,3R)-AHPA(P-OH), which
is then allowed to react with dicyclohexylamine (hereinafter,
benzyloxycarbonyl group is abbreviated as Z).
(2R,3R)-AHPA(p-OH) is benzyloxycarbonylated by benzyl S-4,
6-dimethylpyrimidin-2-yl-t'niocarbonate in the ordinary procedure
to give benzyloxycarbonyl- (2RS,3P~)-AHPA(p-OH), which is then
crystallized as its dicyclohexylamine salt (hereinafter, benzvl-
oxycarbonyl group is abbreviated as Z).
When the salt is selectively recrystallized in organic sol-
vents Z-(2R,3R)-AHPA(p-OH) is obtained. When the filtrate is
concentrated under reduced pressure and the residue is recrystal-
lized from ethyl acetate and ether, the dicyclohexylamine salt
- 12 -
84~1
of optically pure Z-( 2S,3R)-AHPA(p-OH) is obtained. When this
dicyclohexylamine salt is selectively crvstallized the dicyclo-
hexylamine salt of optically pure Z-( 2S,3R)-AHPAtp-OH) is
obtained. The dicyclohexylamine salt of Z-( 2S,3R~-AHPA~p-OH) is
obtained by concentration of the filtrate under reduced pressure
and recrystallization from ethyl acetate and ether.
It was noted that he ( 2P~,3R) -form of Z-AHPA(p-OH) had
smaller solubilities into an organic solvent than the (2S,3R)-
form. Z-(2RS,3R)-AHPA(p-OH) is dissolved in a first soluble
solvent at room temperature or under heating. Then a second in-
soluble solvent is added so as to precipitate crystals, which
are then separated by ~iltration. If necessary, the foregoing
operation is repeated until optically pure Z-( 2P~,3R)-AHPA(p-OH)
is obtained.
The first soluble solvent may include lower alcohols such
as methanol, ethanol and propanol; ethers such as diethyl ether,
diisopropyl ether, tetrahydrofuran and dioxane; esters such as
methyl acetate and ethyl acetate; ketones such as acetone and
methyl ethyl ketone; halogenated hydrocarbons such as methylene
chloride and chloroform; amides such as dimethylformamide and
dimethylacetamide; and nitriles such as acetonitrile, etc. The
second insoluble solvent may include petroleum hydrocarbons
such as petroleum ether, petroleum benzene and ligroin; aromatic
hydrocarbons such as benzene and toluene; alkanes such as pen-
tane and hexane; and cyclohexanes such as cyclopentane and
- 13 -
34~
cyclohexane. By use of the afore-mentioned method em~loying
dicyclohexylamine, the opticall~ im~ure Z-(2S,3R)-AHPA(p-OH)
present in the filtrate may be purified to optically pure Z-(2S,
3R)-AHPA(p-OH).
Z-AHPA(p-OH) as used in the above-mentioned resolution may
be synthesized by Schotten-Baumann method in the presence of an
alkali by reaction of (2RS,3R)-AHPA(p-OH) and benzyloxycarbonyl
chloride or, otherwise, in the presence of an organic tertiary
base such as triethylamine and N-methylmorpholine by reaction
with a benzyloxycarbonylating reagent such as benzyloxycarbonyl-
p-nitrophenyl ester, benzyloxycarbonyl azide, benzyloxycarbonyl-
N-hydroxysuccinimide ester and benzyloxycarbonyl-4,6-dimethyl-
2-mercaptopyrimidine in a solvent ~repared by mixing dioxane,
tetrahydrofuran, acetonitrile or dimethylformamide with water.
Although the foregoing optical resolution has been
described with respect to AHPA(p-OH), a similar optical resolu-
tion may be effected, if necessary, for the other amino acids.
To prepare compounds as represented by Formula (I), an
amino acid as represented by Formula (III) is condensed with a
compound as represented by Formula (IV) in the ordinary pePtide
linking method and then the protecting groups, which, if
necessary have been used for protecting the functional groups
which do not take part in the reaction, are removed.
Typical examples of amino acids are glycine, alanine, 2-
amino-butanoic acid, valine, norvaline, leucine, norleucine,
isoleucine, tertiary-leucine, 2-amino-
3~
34~1
heptanoic acid~ 2-amino-5-methylhexanoic acid, 2-amino-
octanoic acid, 2-amino-6-methylheptanoic acid, serine,
threonine, allothreonine, cysteine, homocysteine, as-
paragine, glutamine, O-methylserine, O-ethylserine,
O-propylserine, methionine3 ethionine, aspartic acid,
glutamic acid, phenylglycine, p-methoxyphenylglycine,
phenylalanine, tyrosine, p-methoxyphenylalanine and p-
nitrophenylalanine.
The method for condensing an amino acid as
represented by Formula (III) and an amino acid as repre-
sented by Formula (IV) includes a carbodiimide method
wherein dicyclohexylcarbodiimide or l-ethyl-~-(3-dimethyl-
aminopropyl)carbodiimide is used; an azide method employ-
ing nitrous acid or alkyl nitrite; a mixed anhydride
method employing ethyl chloroformate or isobutyl chlor)-
~^rmate; an active ester method employing cyanomethyl
ester, vinyl ester, substituted and non-substituted
phenyl esters, thiophenyl ester of N-hydroxysuccinimide
ester; an O-acyl hydroxylamine derivative method employ-
ing O-acylacetoxime or O-acylcyclohexanonneoxime; an
N-acyl derivative method employing carbonyldiimidazole.
Organic solvents using in the above ~onderlsa-
tion reaction may be ethers such as diethyl ether,
tetrahydrofu-ran or dioxane; esters such as ethyl acetate
or methyl acetate; ketones such as acetone or methyl
ethyl ke~tone; halogenated hydrocarbons such as methylene
chloride or chloroform; amides such as dimethylformamide
or dimethylacetamide; nitriles such as acetonitrile.
In the case when an amino acid is represented
by Form~la (III) and whose amino group is protected and
an amino acid as represented by Formula (IV) whose
-15-
4~
carboxyl group is not protected are condensed in an active
ester method, a mixed solvent of water and water miscible
organic solvent may be used in the presence of an inor-
ganic base such as sodium bicarbonate, magnesium oxide
or an organic tertiary base such as triethylamine or
N-methylmorpholine
Protecting groups in the resulting compound may
be removed by the usual method in peptide chemistry such
as catalytic hydrogenation on palladium, saponification
with an alkali, acidolysis with hydrogen bromide in
acetic acid, with trifluoroacetic acid~ with hydrogen
chloride in dioxane, tetrahydrofuran or ethyl acetate~
with liquid hydrogen fluoride, hydrazinolysis with hydra-
zine or treatment with sodium in liquid ammonia. Thus, the
intended substance as represented by Formula (I) ~s ob-
ained.
The nitrile derivatives as represented byFormula (II) and used in this invention as the starting
material may be synthesized reducing an a-amino acid,
whose amino group is belng protected and c,arboxyl group
converted to an amide by reaction with a secondary amine,
at low temperature less than 0 C. with a metal hydride
in ethers such as diethyl ether or tetrahydrofuran to
prepare an amino-aldehyde whose amino group is protected.
The resulting amino-aldehyde is then converted to the
adduct with sodium bisulfite and then allowed to react
with an alkaline metal cyanide or directly allowed to
react with hydrogen cyanide to prepare cyanohydrin, or
3-amino-2-hydroxynitrile.
Preferred examples of the secondary amine are
N,N-dimethylamine, aziridine, N-methylaniline, carbazole,
-16-
3,5-dimethylpyrazole and imidazole~ Preferred exa~les of metal
hydride are lithium aluminum hydride, lithium di- and tri-
alkoxyaluminum hydride and sodium bis~2-methoxyethoxy)aluminum
hydride. Examples of the protecting group for the amino group
are the protecting groups usually employed in the peptide chem-
istry. Urethane type protecting groups may be used preferably and
above all, benzyloxycarbonyl grou3 may be preferred.
According to a second method a lower alkyl ester of a_
amino acid whose amino group is protected by an amino-protecting
group similar to those mentioned previously is reduced at a
temperature lower than -40 C. in aromatic hydrocarbons such as
toluene or benzene and ethers such as diethyl ether or tetra-
hydrofuran with metal hydrides such as sodium aluminum hydride,
diisobutylaluminum or sodium bis(2-methoxyethoxy)aluminum hydride
thereby to prepare aminoaldehyde whose amino group is protected.
When such an aminoaldehyde has been treated in the above-
mentioned manner, 3-amino-2-hydroxynitriles are pre~ared.
Following is a discussion by way of example only of methods
of carrying the invention into effect. However, it should be
noted herein that any suitable functional group-protecting
methods, functional group-removing methods and peptide linkage-
forming methods other than those described hereinbelow may be
employed. In addition to the aforementioned abbreviations, the
following abbreviations may be used in the examples:
HOBt, N-hydroxybenzotriazole; DCCD, N,N'-dicyclohexylcarbodi-
imide; HOSu, N-hydroxysuccinimide; -OBzl.TosOH, benzyl ester p-
toluenesulfonate; -OSu, N-hydroxysuccinimide ester; -OMe,
17
34~
methyl ester; -ONb, p-nitrobenzyl ester; Boc, t-butoxycarbonyl;
DCHA, dicyclohexylamine, -Osut tert.-butyl ester.
Rf value is measured on a silica gel GF254 ~late prepared by
Merck Corp. using n BuOH: AcOH: H2O (4:1:1) as developing
solvent.
A few 3-amino-2-hydroxYcarboxylic acids and their contain-
ing peptides possess two Rf values because they are a mixture of
threo- and erythro- configurations.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Example 1
Step 1
22.0 g. of oily Z-(2RS,3RS)-3-amino-2-hydroxy-4-p-methoxy-
phenylbutyronitrile was dissolved in a mixture of 200 ml. of
concentrated hydrochloric acid and 200 ml. of dioxane. After
adding 13.2 g. of anisole the reaction mixture was refluxed for
12 hours. Then the dioxane was distilled away under reduced
pressure, the resulting solution of hydrochloric acid washed
with ether and the water layer concentrated under reduced
pressure and evaporated to drvness. Subsequently, 100 ml. of
water was added to the residual substance and the insoluble sub-
stance was separated by filtration. After adding an equal
quantity of acetone the mixture was adjusted to pH 5.5 with
am~onia water. The mixture was allowed to stand in a refriger-
ator. The deposited crystals were separated by filtration to
obtain 6.73 g. of intended (2RS,3RS)AHPA(p-OH).
- 18 -
1~184~1
Step 2
2.11 g. of (2~S,3RS)-AHPAtp-OH) obtained in Ste~ 1 was
dissolved in 10 ml. of lN sodium hydroxide solution. While
vigorously agitating the solution under coolin~ with ice, 4.5
ml. of Z-Cl was added in three portions over a period of 30
minutes. Then the reaction mixture was vigorously agitated for
1 hour under cooling with ice and for 3 hours at room temper'a-
ture. During the reaction the pH was adjusted to 8-9 with lN
sodium hydroxide solution.
T~hen the reaction had been com~leted, 6N hydrochloric acid
was added to adjust the reaction mixture to pH 2. As a result
oily material separated which was then extracted twice with 100
ml. of ethyl acetate. The ethyl acetate layer was washed with
water and dehydrated to dryness by the use of anhydrous magnes-
ium sulfate. After separating magnesium sulfate by filtration
the filtrate was concentrated under reduced pressure and the
residue crystallized in ethyl acetate-petroleum ether to provide
3.64 g. of Z-(2RS,3RS)-AHPA(P-OZ). M.p. 138-140 C.
-- 19 --
,~. . .
11184 ~1
Step 3
479 mg. of Z-(2RS,3RS)-AHPA(P-OZ) and 162 mg.
of HOBt were dissolved in 10 ml. of tetrahydrofuran.
After adding 472 mg. of Leu-OBzl-TosOH the mlxture was
neutralized with 0.168 ml. of triethylamine and cooled
to -5 C. Then 206 mg. of DCCD was added and the reac-
tion mixture was allowed to stand overnight for reaction.
~-~rahydrofuran was distilled away under reduced pressure
and ~0 ml. of ethyl acetate was added. After filtering
off the insoluble substances the filtrate was washed with
lN sulfuric acid, water, 5% aqueous sodium bicarbonate
solution and water in that order and then dehydrated to
dryness with anhydrous magnesium sulfate. The residue
obtained by concentrating the filtrate under reduced
pressure was solidified in ethyl acetate-petroleum ether.
Recrystallization from the same solvent gave 450 mg. of
Z-(2RS,3RS)-AHPA(P-OZ)-(S)-Leu-OBzl. M.p. 98-99 C.,
[a]5788 -14-0 (c o.58, AcOH).
Step 4
400 mg. of Z-(2RS,3RS)-AHPA(P-OZ)-(S)-Leu-OBzl
was dissolved in 10 ml. of methanol and hydrogenated for
3 hours with about 10 mg. of palladium black. The
catalyst was filtered off and the solvent was concentrated
under reduced pressure. When a recrystallization opera-
tion was carried oùt with methanol-ethyl acetate, 219 mg.
of (2RS,~RS)-3-amino-2-hydroxy-4-p-hydroxyphenylbutanoyl-
(S) leucine were obtained.
[a]3578 -8~8(c 0.90, AcOH),
Rf o.48 and 0.51, An~l. for C16H24N205,
Found: C~ 59.38; H, 7.23; N, 8.95. Calc'd.: C, 59.24;
H, 7.46; N, 8.64.
-20-
113 8441
xample 2
When 30 g. of Z-~2RS,3R~3~amino-2-hydroxy-4-
p-hydroxyphenylbutyronitrile was treated in similar manner
to Example 1, Step 1, 12.61 g. of (2RS,3R)-AHPA(p-OH) was
obtained.
Rf 0.20 Anal. for CloH12NO4,
H, 5.99; N, 7.43. Calc'd.: C, 58.81; H, 5.92; N, 7.82.
When (2RS,3R~-AHPA(p-OH) was benzyloxycarbonylated
using benzyl-S-4,6-dimethylpyrimidin-2-ylthiocarbonate,
Z-AHPA(p-OH) was obtained as DCHA salt. 15.22 g. of that crude
DCHA salt was crystallized from methanol, ethyl acetate and
petroleum ether and 3.2 g. of optically impure Z-(2R,3R)-
AHPA(p-OH) DCHA salt was obtained as a first crop.
When the mother liquor was evaporated to dryness
and the residue precipitated three times from ethyl acetate
and ether, 5.02 g. of optically pure Z-(2S,3R)-AHPA(p-OH)DCHA
salt was obtained.
M.p. 121-122C., [~]578 + 49 9 (c 0.87, AcOH);
Anal. for C30H42N2O6, Found: C, 69.81; H, 8-35; N, 6-42-
Calc'd.: C, 69.46; H, 8.16; N, 6.17.
After a treatment of Z-(2S,3R)-AHPA(p-OH) DCHA
salt (1.05 g.) with ethyl acetate and dilute H2SO4, the
obtained Z-(2S,3R)-AHPA(p-OH), 866 mg. of (S)-Leu-OBzl TosOH,
405 my. of HOBt, 0.308 ml. of triethylamine and 412 mg. of
DCCD were treated in similar manner to Example 1, Step 3.
Oily Z-(2S,3R)-AHPA(p-OH)-(S)-Leu-OBzl was obtainea quan-
titatively~
When the obtained oily Z-(2S,3R)-AHPA(p-OH)-(S)-
Leu-OBzl was treated in similar manner to Example 1,
Step 4, 630 mg. of (2S,3R)-3-amino-2-hydroxy-4-p-hydroxy-
- 21 -
11184~1
phenylbutanol-(S)-leucine was obtained.
~ ~-7578 -19-9 (c~ 1.19, AcOH)
Rf 0.48, Anal. for C16H23N2O5, Found C, 59.98; H, 7.42;
N, 10.42. Calc'd: C, 60.55; H, 7.30; N, 10.08.
The physiological activities o~ Bestatin and two compounds
represented by Formula (I) prepared in the present invention
were determined as follows:
(A) Inhibitory activity against aminopeptidase B Testing
method:
The method described by V. K. Hopusu, K. K. Makinen,
G. G. Glenner in Archives of Biochemistry and Biophysics 114,
557, (1966) was modified. To the mixture of 0.3 ml. of 1 mM
arginine ~ -naphthylamide and 1.0 ml. of 0.1 M Tris hydro-
chioride buffer (pH 7.0), 0.7 ml. of distilled water with or
without a test material is added and warmed at 37 C. for 3
minutes. The reaction is started by addition of 0.2 ml. of
aminopeptidase B solution which is prepared by Sephadex* 100
chromatography as described by Hopusu et al. After 30 minutes
at 37 C., 0.6 ml. of l.OM acetate buffer (pH 4.2) containing
diazonium salt of o-aminoazotoluene at 1.0 m~./ml. and Tween* 20
at 1.0% is added. Fifteen minutes at room temperature there-
after, absorbance (a) at 530 nm is measured by spectrophotometer.
As the control, by similar means the absorbance (b) after the
reaction in the absence of a sample is measured. me inhibition
percent is calculated as follows: (b-a)/b x 100.
Inhibition percentages at various concentrations were
measured and from the measured inhibition percentages, 50%
inhibitions (ID50) were deduced. The results are as listed in
Table 1.
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1~184 ~1
Table 1
Compounds 50 (mcg./ml.)
Example 1 0.10
Example 2 0.007
Bestatin [(2S,3R~-AHPA-(S~-Leu~ 0.10
As you will see from the table the compound of
Example 1 has substantially the same inhibitory effects
as Bestatin but the compound of Example 2 can attain the
same effect in a far less amount, one-fourteenth of
Bestatin. Gathering from these results, it is expected
that the new compounds, especially the compound of
Example 2 which is an optically active form of the com-
pound of Example 1, can be an extremely useful physio
logically active substance.
(B~ The compound of Example 1 was also tested for
its humoral antibody formation to find its efficaGy as an
immunizing cancer inhibitor. As a result, it was found
that the compound has an effect of increasing the number
of humoral antibody cells to a considerable degree. The
results suggest that the compound can serve as an excel-
lent immunizing cancer inhibitor. For the humoral anti-
body formation of Bestatin per se see J. Antibiotics,
29(8), 857-859 (August, 1976~.
The effect of (2RS,3RS)-3-amino-2-hydroxy-4-p-
hydroxyphenylbutanoyl-(S)-leucine on humoral antibody
formation to Sheep Red Blood Cell (SRBC~ in mice was
studied as follows.
Mice (dd/y female) were immunized by intravenous
injection of 10 SRBC. Intraperitoneal injection of
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44~
(2RS,3RS)-3-amino-2-hydroxy-4-p~hydroxyphenylbutanoyl-(S)-
leucine was made soon afterwards.
Bestatin [(2S,3R~-3-amino-2-hydroxy-4-phenyl-
butanoyl-(S)-leucine] and (2RS,3RS)-3-amino-~-hydroxy-4-
p-chlorophenylbutanoyl-(S~-leucine were used as control.
Four days thereafter the number of plaque forming
cells in the spleen were enumerated by JERNE's hemo-
lytic plaque technique [Jerne, N.K.; A. A. Nordin & C.
Henry: "The Agar Plaque Technique for Recognizing Anti-
body-producing Cells" in cell-bound antibodies (Wistar
Institute Press, Philadelphia, 1963~, pp. 109-122].
The results are as listed in Table 2.
Table 2
Effect of (2RS,3RS~-3-amino-2=hydroxy-4-p-hydroxyphenyl-
butanoyl-(S)-Leucine on Humoral Antibody Formation to
SRBC in Mice
Antibody Forming CeIls
Treated Group
Non-treated
Name of Compound Dose Number Group
- - 12,500+ 9,050
(2RS,3RS)-3-amino- 1 mg. 207,400_ 8,025 1.66
2-hydroxy-4-p- 100 mcg 261,000+11,700 2.09
hydroxyphenylbuta-
noyl-(S)-leucine10 mcg. 208,000+ 7,180 1.66
1 mcg. 175,800+ 8,200 1.41
0.1 mcg. 141,000+ 5,700 1.13
Bestatin 1 mg. 190,000+ 7,100 1.52
10 mcg. 136,250+ 6,500 1.09
(2RS,3RS)-3-amino- 1 mg. 208,750+ 8,000 1.67
2-hydroxy-4-p-10 mcg. 133,750+ 5,600 1.07
chlorophenyl-
butanoyl-(S)-
Leucine
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~1~84'~1
The number of antibody forming cells in mice group
given 10 mcg. of Bestatin or ~2RS,3RS~-3-amino-2-hydroxy-4-
p-chlorophenylbutanoyl-(S~-leucine was nearly equal to that
of non-treated group.
On the other hand the number of antibody forming
cells in mice given 10 mcg. of (2RS,3RS~-3-amino-2-hydroxy-
4-p-hydroxyphenylbutanoyl-(S~-leucine was 1.66 times larger
than that of the non-treated mice and even when given only
1 mcg. it showed 1.41 times.
As mentioned above (2RS,3RS~-3-amino-2 hydroxy-
4-p-hydroxybutanoyl-(S)-leucine has the excellent effect of
increasing the number of antibody forming cells and did
not increase the weight of the spleen or the number of
nonspecific antibody forming cell.s.
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1~18441
'Re'fe'renc'e Example 1
Synthesis of Nitr le'From A'l'dehyde
A solution consisting of 20.8 g. of sodium hydrogen
sulfite and 50 ml. of water is added to about 52.7 g. of oily
Z-(R)-phenylalaninal and separated adduct is filtered
off and washed with water and ether in this order to prepare
77 g . of crude 3-benzyloxycarbonylamino-2-hydroxy-4-
phenylbutyronitrile. 68 G. of resulting adduct is suspended
in 250 ml. of water and cooled to 10-12C. After adding
500 ml. of ether, a solution consisting of 13 g. of potassium
cyanide and 100 ml. of water is added dropwise over 30 minutes.
Then the reaction mixture is allowed to react
for 3 hours at room temperature and the water layer is dis-
carded. The ether layer is washed with an aqueous solution of
sodium chloride and dehydrated to dryness over anhydrous
magnesium sulfate.
When magnesium sulfate is filtered off and ether
is distilled away under reduced pressure, 49 g. of oily
benzyloxycarbonyl-(2RS,3R)-3-amino-2-hydroxy-4-phenylbutyro-
nitrile is obtained.
Nitrile derivatives used in the present inventionare prepared in the same manner.
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