Acid derivatives

The invention concerns allophanic acid derivatives of formula I EQU R.sup.1 --N(R.sup.2)CO--N(R.sup.3)CO--X.sup.1 --Q--X.sup.2 --GI and pharmaceutically acceptable metabolically labile esters or amides thereof, and pharmaceutically acceptable salts thereof, in which R.sup.1, R.sup.2, R.sup.3, X.sup.1, Q, X.sup.2 and G have the meanings given in the specification. The invention also concerns processes for the preparation of the allophanic acid derivatives of formula I, pharmaceutical compositions containing them and their use as inhibitors of the binding of fibrinogen to glycoprotein IIb/IIIa.

The present invention relates to a group of chemical compounds which 
inhibit cell adhesion (for example platelet aggregation), to processes for 
their preparation and to pharmaceutical compositions containing them. 
A variety of diseases involve cell adhesion during their development. For 
example, platelet aggregation is involved in the formation of blood 
thrombi, which can lead to diseases such as thrombosis, (for example 
stroke and thrombotic events accompanying unstable angina and transient 
ischaemic attack), myocardial infarction, atherosclerosis, thromboembolism 
and reocclusion during and after thrombolytic therapy. 
It is widely believed that the platelet membrane glycoprotein IIb-IIIa 
(GPIIb-IIIa) mediates platelet aggregation. Adhesion molecules such as 
fibrinogen and von Willebrand Factor are believed to bind to GPIIb-IIIa 
sites on adjacent platelets and thereby cause them to aggregate. Other 
adhesion molecules which are known to bind to GPIIb-IIIa are fibronectin, 
vitronectin and thrombospondin. 
Compounds which inhibit platelet aggregation and the binding of adhesion 
molecules to GPIIb-IIIa are known, for example from U.S. Pat. Nos. 
5,039,805 and 5,084,466, Canadian patent applications numbers 2,008,161, 
2,037,153 and 2,061,661, and Alig et al., J. Med. Chem., 1992, 35, 
4393-4407. Commonly the structures of these compounds are based upon the 
binding regions of the adhesion molecules, which are peptides. For 
example, a portion of fibrinogen which is believed to bind to GPIIb-IIIa 
is the amino acid sequence RGD (arginyl glycyl aspartate). 
The ability to inhibit platelet aggregation and to inhibit the binding of 
fibrinogen to GPIIb-IIIa has now been found to be possessed by certain 
acid derivatives containing an allophanoyl group. 
According to one aspect, therefore, the present invention provides a 
compound of the general formula I (formula set out at the end of the 
description together with the other formulae referred to herein by Roman 
numerals) 
wherein R.sup.1 represents a group of formula II or III in which A is 
attached meta or para to the position where the group NR.sup.2 CONR.sup.3 
CO is attached and is selected from aminomethyl, guanidino and R.sup.a 
N.dbd.C(NH.sub.2)-- where R.sup.a is hydrogen or phenyl which is 
unsubstituted or substituted by 1 or 2 of halogeno, (1-4C)alkyl, 
(1-4C)alkoxy, cyano and nitro, 
E is CH or N, 
Z.sup.1 is hydrogen, halogeno, (1-4C)alkyl, (1-4C)alkoxy, cyano or nitro, 
T is N or CH, and 
X.sup.3 is a bond, (1-4C)alkylene or, when T is CH, oxy(1-3C)alkylene; 
R.sup.2 and R.sup.3, which may be the same or different, represent 
hydrogen, (1-4C)alkyl or ar(1-4C)alkyl; 
X.sup.1 is a bond or (1-4C)alkylene; 
Q is a group of formula IV or V in which Z.sup.2 is hydrogen, halogeno, 
(1-4C)alkyl, (1-4C)alkoxy, cyano or nitro, and 
Z.sup.3 is a group of formula X.sup.2 --G.sup.a in which X.sup.2 can have 
any of the values given hereinafter for X.sup.2 and G.sup.a can have any 
of the values given hereinafter for G, or G.sup.a has any of the values 
given hereinbefore for Z.sup.2 ; 
X.sup.2 is a bond, (1-4C)alkylene, oxy(1-3C)alkylene or a group of formula 
CH.sub.2 CH(NHXR.sup.4) in which X is SO.sub.2, CO or CO.sub.2 and R.sup.4 
is (1-6C)alkyl, (6-12C)aryl or (6-12C)aryl(1-4C)alkyl, in any of which the 
aryl group may optionally be substituted by (1-4C)alkyl; and 
G is a carboxy group or a pharmaceutically acceptable metabolically labile 
ester or amide thereof; and 
pharmaceutically acceptable salts thereof. 
It will be appreciated that depending on the nature of the substituents, in 
containing one or more chiral centres, the formula I compounds may exist 
in and be isolated in one or more different enantiomeric or racemic forms 
(or a mixture thereof). It is to be understood that the invention includes 
any of such forms which possesses the property of inhibiting platelet 
aggregation and inhibiting the binding of fibrinogen to GpIIb-IIIa, it 
being well known how to prepare individual enantiomeric forms, for 
example, by synthesis from appropriate chiral starting materials or by 
resolution of a racemic form. Similarly, the biological properties of a 
particular form may be readily evaluated, for example by use of one or 
more of the standard in vitro or ex vivo screening tests detailed 
hereinbelow. 
It will also be appreciated that compounds of formula I wherein R.sup.1 
represents a group of formula II and A represents the group R.sup.a 
N.dbd.C(NH.sub.2)-- may exist in tautomeric forms, and that the invention 
includes the compounds in any of their tautomeric forms. 
A is preferably a group of formula R.sup.a N.dbd.C(NH.sub.2)--. It is 
preferably attached para to the position where the group NR.sup.2 
CONR.sup.3 CO is attached. 
Examples of values for Ra include hydrogen and phenyl. Examples of 
substituents on R.sup.a when it is phenyl include fluoro, chloro, bromo, 
methyl, ethyl, methoxy, ethoxy, cyano and nitro. 
When R.sup.1 represents a group of formula II bearing the substituent 
Z.sup.1, Z.sup.1 may represent, for example, hydrogen, fluoro, chloro, 
bromo, methyl, ethyl, methoxy, ethoxy, cyano or nitro. 
When R.sup.1 represents a group of formula III examples of values for 
X.sup.3 include a bond, methylene, ethylene, trimethylene and, when T is 
CH, oxymethylene. Examples of values for R.sup.1 include 
3-aminomethylphenyl, 4-aminomethylphenyl, 4-amidinophenyl, 4-(N.sup.2 
-phenyl)amidinophenyl, 6-amidinopyrid-3-yl, 5-amidinopyrid-2-yl, 
piperidin-4-yl, piperidin-4-ylmethyl, 2-piperidin-4-ylethyl, 
piperidin-4-yloxymethyl and piperazin-1-yl. 
A (1-4C)alkyl group represented by R.sup.2 or R.sup.3 may be, for example, 
methyl or ethyl. An ar(1-4C)alkyl may be, for example, benzyl. Preferably 
one of R.sup.2 and R.sup.3 is hydrogen and the other is hydrogen, methyl 
or benzyl. More preferably each of R.sup.2 and R.sup.3 represents 
hydrogen. 
Examples of values for X.sup.1 when it represents (1-4C)alkylene are 
methylene and ethylene. Preferably X.sup.1 represents a bond. 
In the group Q, when it is a group of formula IV, examples of values for 
Z.sup.2 include hydrogen, fluoro, chloro, bromo, methyl, ethyl, methoxy, 
ethoxy, cyano and nitro. Hydrogen is a preferred value for Z.sup.2. 
In the group Q, when it is a group of formula IV or V, and Z.sup.3 is a 
group of formula X.sup.2 --G.sup.a, examples of values for X.sup.2 include 
a bond, methylene, ethylene, oxymethylene and groups of formula CH.sub.2 
CH(NHXR.sup.4) in which X is SO.sub.2, CO or CO.sub.2 and R.sup.4 is 
methyl, ethyl, propyl, butyl, pentyl, phenyl, tolyl or benzyl, and 
examples of values for G.sup.a include carboxy (or a pharmaceutically 
acceptable metabolically labile ester or amide thereof), hydrogen, fluoro, 
chloro, bromo, methyl, ethyl, methoxy, ethoxy, cyano and nitro. Preferably 
Z.sup.3 is hydrogen or a group of formula X.sup.2 --G.sup.a in which 
X.sup.2 is oxymethylene and G.sup.a is carboxy. 
Examples of values for X.sup.2 include a bond, methylene, ethylene, 
oxymethylene, oxyethylene and groups of formula CH.sub.2 CH(NHXR.sup.4) in 
which X is SO.sub.2, CO or CO.sub.2 and R.sup.4 is methyl, ethyl, propyl, 
butyl, pentyl, phenyl, tolyl or benzyl. Preferably X.sup.2 is oxymethylene 
or a group of formula CH.sub.2 CH(NHSO.sub.2 (CH.sub.2).sub.3 CH.sub.3). 
Examples of ester derivatives of a carboxy group represented by G include 
esters formed with alcohols such as (1-6C)alkanols, for example methanol, 
ethanol, propanol and t-butanol; indanol; benzyl alcohol; adamantol; 
(1-6C)alkanoyloxy(1-4C)alkanols such as pivaloyloxymethanol; glycolamides; 
(5-methyl-2-oxo-1,3-dioxol-4-yl)methyl alcohol; and 
(1-4C)alkoxycarbonyl(1-4C)alkanols. 
Examples of amide derivatives of a carboxy group represented by G include 
amides derived from amines such as (1-4C)alkylamines, for example 
methylamine; di(1-4C)alkylamines, for example dimethylamine; 
(1-4C)alkoxy(1-4C)alkylamines such as methoxyethylamine; and amino acids 
such as glycine or an ester thereof. 
Preferably G represents a carboxy group or a (1-4C)alkoxycarbonyl group 
such as methoxycarbonyl, ethoxycarbonyl or t-butoxycarbonyl. 
Particular pharmaceutically acceptable salts include, for example, salts 
with acids affording physiologically acceptable anions, such as salts with 
mineral acids, for example a hydrogen halide (such as hydrogen chloride 
and hydrogen bromide), sulphuric acid or phosphoric acid, and salts with 
organic acids, for example acetic acid and trifluoroacetic acid. Other 
pharmaceutically acceptable salts include, for example salts with 
inorganic bases such as alkali metal and alkaline earth metal salts (for 
example sodium salts), ammonium salts, and salts with organic amines and 
quaternary bases forming physiologically acceptable cations such as salts 
with methylamine, dimethylamine, trimethylamine, ethylenediamine, 
piperidine, morpholine, pyrrolidine, piperazine, ethanolamine, 
triethanolamine, N-methylglucamine, tetramethylammonium hydroxide and 
benzyltrimethylammonium hydroxide. 
Particular compounds of the invention include, for example, allophanic acid 
derivatives of formula I, or pharmaceutically acceptable salts thereof, in 
which, unless otherwise stated, each of the variable groups R.sup.1, 
R.sup.2, R.sup.3, X.sup.1, Q, X.sup.2 and G have any of the meanings 
defined hereinbefore or in this section concerning particular compounds of 
the invention: 
(a) R.sup.1 represents a group of formula II in which A is attached para to 
the position where the group NR.sup.2 CONR.sup.3 CO is attached and is 
selected from aminomethyl, guanidino and R.sup.a N.dbd.C(NH.sub.2)-- where 
R.sup.a is hydrogen or phenyl, E is CH or N, and Z.sup.1 is hydrogen, 
fluoro, chloro, methyl, methoxy or cyano; 
(b) R.sup.1 represents a group of formula III in which T is CH or N, and 
X.sup.3 is a bond, methylene, ethylene, trimethylene or, when T is CH, 
oxymethylene; 
(c) R.sup.2 and R.sup.3 which may be the same or different represent 
hydrogen, methyl, ethyl or benzyl; 
(d) X.sup.1 is a bond or methylene; 
(e) Q is a group of formula IV in which Z.sup.2 is hydrogen, fluoro, 
chloro, methyl, methoxy or cyano, and Z.sup.3 is hydrogen or a group of 
formula X.sup.2 --G.sup.a in which X.sup.2 is methylene, ethylene or 
oxymethylene and G.sup.a is a carboxy group or a pharmaceutically 
acceptable metabolically labile ester thereof; 
(f) Q is a group of formula V in which Z.sup.3 is hydrogen or a group of 
formula X.sup.2 --G.sup.a in which X.sup.2 is methylene, ethylene or 
oxymethylene and G.sup.a is a carboxy group or a pharmaceutically 
acceptable metabolically labile ester thereof; 
(g) X.sup.2 is methylene, ethylene or oxymethylene; and 
(h) G is a carboxy group or a pharmaceutically acceptable metabolically 
labile ester thereof. 
A preferred compound of the invention is an allophanic acid derivative of 
formula I wherein 
R.sup.1 represents a group of formula II in which A is attached para to the 
position where the group NR.sup.2 CONR.sup.3 CO is attached and is 
selected from aminomethyl and a group of formula R.sup.a 
N.dbd.C(NH.sub.2)-- where R.sup.a is hydrogen or phenyl, 
E is CH and Z.sup.1 is hydrogen, fluoro, chloro, methyl or methoxy; 
R.sup.2 is hydrogen, methyl or benzyl; 
R.sup.3 is hydrogen, methyl or benzyl; 
X.sup.1 is a bond; 
Q is a group of formula IV in which Z.sup.2 is hydrogen, fluoro, chloro, 
methyl or methoxy, and Z.sup.3 is hydrogen or a group of formula X.sup.2 
--G.sup.a in which X.sup.2 is oxymethylene and G.sup.a is carboxy, 
methoxycarbonyl or ethoxycarbonyl; 
X.sup.2 is oxymethylene; and 
G is carboxy, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl or 
t-butoxycarbonyl; 
or a pharmaceutically acceptable salt thereof. 
A further preferred compound of the invention is an allophanic acid 
derivative of formula I wherein 
R.sup.1 represents a group of formula III in which T is CH or N, and 
X.sup.3 is a bond, methylene, ethylene or, when T is CH, oxymethylene; 
R.sup.2 is hydrogen, methyl or benzyl; 
R.sup.3 is hydrogen, methyl or benzyl; 
X.sup.1 is a bond; 
Q is a group of formula IV in which Z.sup.2 is hydrogen, fluoro, chloro, 
methyl or methoxy, and Z.sup.3 is hydrogen or a group of formula X.sup.2 
--G.sup.a in which X.sup.2 is oxymethylene and G.sup.a is carboxy, 
methoxycarbonyl or ethoxycarbonyl; 
X.sup.2 is oxymethylene; and 
G is carboxy, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl or 
t-butoxycarbonyl; 
or a pharmaceutically acceptable salt thereof. 
A further preferred compound of the invention is an allophanic acid 
derivative of formula I 
wherein R.sup.1 represents a group of formula II in which A is attached 
para to the position where the group NR.sup.2 CONR.sup.3 CO is attached 
and is a group of formula R.sup.a N.dbd.C(NH.sub.2)-- where R.sup.a is 
hydrogen, 
E is CH and Z.sup.1 is hydrogen; 
R.sup.2 is hydrogen; 
R.sup.3 is hydrogen or methyl; 
X.sup.1 is a bond; 
Q is a group of formula IV in which Z.sup.2 is hydrogen and Z.sup.3 is 
hydrogen or a group of formula X.sup.2 --G.sup.a in which X.sup.2 is 
oxymethylene and G.sup.a is carboxy; 
X.sup.2 is oxymethylene; and 
G is carboxy, methoxycarbonyl, ethoxycarbonyl or t-butoxycarbonyl; 
or a pharmaceutically acceptable salt thereof. 
A further preferred compound of the invention is an allophanic acid 
derivative of formula I wherein 
R.sup.1 represents a group of formula III in which T is CH and 
X.sup.3 is ethylene; 
R.sup.2 is hydrogen; 
R.sup.3 is hydrogen or methyl; 
X.sup.1 is a bond; 
Q is a group of formula IV in which Z.sup.2 is hydrogen and Z.sup.3 is 
hydrogen or a group of formula X.sup.2 --G.sup.a in which X.sup.2 is 
oxymethylene and G.sup.a is carboxy; 
X.sup.2 is oxymethylene; and 
G is carboxy, methoxycarbonyl, ethoxycarbonyl or t-butoxycarbonyl; 
or a pharmaceutically acceptable salt thereof. 
Specific especially preferred compounds of the invention include allophanic 
acid derivative of formula I selected from: 
methyl 4-[4-(4-amidinophenyl)allophanoyl]phenoxyacetate and 
4-[4-(4-amidinophenyl)allophanoyl]phenoxyacetic acid; 
or a pharmaceutically acceptable salt thereof. 
The compounds of formula I, the metabolically labile esters and amides 
thereof, and the pharmaceutically acceptable salts thereof may be prepared 
by procedures analogous to procedures known in the art for the preparation 
of structurally analogous compounds. Such procedures are included as a 
further feature of the invention and include the following preferred 
procedures for the manufacture of a compound of the formula I in which 
R.sup.1, R.sup.2, R.sup.3, X.sup.1, Q, X.sup.2 and G have any of the 
meanings defined above: 
(A) For a compound of formula I in which G is carboxy, deprotecting a 
compound of formula VI in which G.sup.1 is a carboxy protecting group. 
G.sup.1 may be any conventional carboxy protecting group that may be 
removed without interfering with other parts of the molecule. Examples of 
carboxy protecting groups include (1-6C)alkyl groups (such as methyl, 
ethyl, propyl or t-butyl), phenyl and benzyl, the phenyl moiety in any of 
which may optionally bear 1 or 2 of halogeno, (1-4C)alkyl, (1-4C)alkoxy or 
nitro. 
The deprotection may be carried out using any one or more of the 
conventional reagents and conditions known in the art for converting 
carboxylic esters into carboxylic acids. Thus, for example, the 
deprotection may conveniently be performed by base catalysed hydrolysis, 
for example by using an alkali metal hydroxide such as lithium, potassium 
or sodium hydroxide, or a tertiary amine such as triethylamine, in the 
presence of water. The base catalysed hydrolysis may conveniently be 
performed in the presence of a solvent such as an alcohol, for example 
methanol or ethanol, or an ether such as tetrahydrofuran or dioxan. 
Alternatively the deprotection may be carried out by acid catalysed 
hydrolysis, for example using acetic acid or trifluoroacetic acid. 
Suitable solvents for the acid catalysed hydrolysis include alcohols such 
as those mentioned above, halogenated hydrocarbons such as 
dichloromethane, ethers such as anisole, and water. The temperature is 
conveniently in the range of from -10.degree. to 100.degree. C., for 
example from 10.degree. to 50.degree. C. When the alcohol residue is 
t-butyl, this may also conveniently be removed by heating, for example at 
a temperature in the range of from 80.degree. to 150.degree. C., alone or 
in the presence of a suitable diluent such as diphenyl ether or diphenyl 
sulphone. 
It will be appreciated that a compound of formula I in which G represents 
carboxy and Q represents a group of formula IV or V wherein Z.sup.3 
represents a group of formula X.sup.2 --COOH may be prepared by this 
process starting from a compound of formula VI in which Q represents a 
group of formula IV or V and Z.sup.3 represents a group of formula X.sup.2 
--COOH or X.sup.2 --COOG.sup.1. 
(B) For a compound of formula I in which R.sup.1 is a group of formula II 
and A is an aminomethyl or an amidino group, deprotecting a compound of 
formula VII in which A.sup.1 is a protected aminomethyl or amidino group. 
A.sup.1 may be any conventional protected aminomethyl or amidino group that 
may be deprotected without interfering with other parts of the molecule. 
Examples of protecting groups include oxycarbonyl groups such as 
t-butoxycarbonyl and benzyloxycarbonyl. 
The deprotection may be carried out using any one or more of the 
conventional reagents and conditions known in the art for removing amine 
protecting groups. A t-butoxycarbonyl group may be removed by hydrolysis, 
for example by acid catalysed hydrolysis using an acid such as 
trifluoroacetic acid. Suitable solvents include halogenated hydrocarbons 
such as dichloromethane. A benzyloxycarbonyl group may conveniently be 
removed, for example, by hydrogenation in the presence of a palladium 
catalyst such as palladium on charcoal. The temperature is conveniently in 
the range of from -10.degree. to 100.degree. C., for example from 
10.degree. to 50.degree. C. 
In some cases the reaction conditions required to perform process (A) are 
the same as those required to perform process (B). In such cases it is 
possible to perform processes (A) and (B) at the same time by starting 
with a compound having an appropriate carboxy protecting group and an 
appropriately protected aminomethyl or amidino group. Such a compound is 
represented by the formula VIII. 
(C) For a compound of formula I in which R.sup.2 and R.sup.3 represent 
hydrogen atoms, reacting an isocyanate of formula IX with an amine of 
formula X. 
Suitable solvents include halogenated hydrocarbons such as dichloromethane 
and nitriles such as acetonitrile. The reaction is conveniently performed 
at a temperature in the range of from -10.degree. to 100.degree. C. 
(D) For a compound of formula I in which X.sup.2 is a group of formula 
CH.sub.2 CH(NHXR.sup.4), reacting a compound of formula XI in which 
X.sup.2a is CH.sub.2 CH(NH.sub.2), or an acid addition salt thereof, with 
a compound of formula XII in which U.sup.1 is a leaving atom or group. 
Examples of values for U.sup.1 include halogen such as chlorine or bromine 
and hydrocarbylsulphonyloxy such as methanesulphonyloxy and 
p-toluenesulphonyloxy. Examples of acid addition salts include for 
example, the hydrochloride. The reaction may conveniently be effected at a 
temperature in the range of from -10.degree. to 120.degree. C. preferably 
from 10.degree. to 100.degree. C. Suitable solvents include for example 
ethers such as tetrahydrofuran, amides such as dimethylformamide, nitriles 
such as acetonitrile, halogenated hydrocarbons such as dichloromethane and 
alcohols such as ethanol. The reaction is conveniently performed in the 
presence of a base, for example a tertiary amine such as triethylamine. 
(E) For a compound of formula I in which R.sup.1 is a group of formula II 
and A is a group of formula R.sup.a N.dbd.C(NH.sub.2)--, reacting a 
compound of formula XIII, in which U.sup.2 is a leaving atom or group, 
with a compound of formula R.sup.a NH.sub.2, or an acid addition salt 
thereof. 
Examples of values for U.sup.2 include (1-4C)alkylthio groups such as 
methylthio. Suitable media for the reaction include alcohols such as 
methanol or ethanol, and halogenated hydrocarbons such as dichloromethane. 
The reaction is conveniently performed at a temperature in the range of 
from -10.degree. to 100.degree. C. An acid addition salt of a compound of 
formula R.sup.a NH.sub.2 may be for example, an addition salt of an 
organic acid such as acetic acid or an inorganic acid such as hydrochloric 
acid. 
The intermediates used in the aforementioned processes are either known or 
may be prepared by methods analogous to methods known for preparing known 
compounds. In general, the intermediates containing an acylureido group 
may be prepared by reacting the appropriate isocyanate derivative with the 
appropriate amine. 
Thus, the compounds of formula VI in which R.sup.2 and R.sup.3 represent 
hydrogen may be prepared by reacting an isocyanate of formula XIV with an 
amine of formula X by a method analogous to that of process (C) described 
hereinabove. 
The compounds of formula VI in which R.sup.1 is a group of the formula II 
and A is an aminomethyl group may also be prepared by selectively 
deprotecting a compound of formula VIII. Similarily, the compounds of 
formula VII may also be prepared by selectively deprotecting a compound of 
formula VIII. 
The compounds of formula VIII in which R.sup.2 and R.sup.3 represent 
hydrogen may be prepared by reacting an amine of formula XV with an 
isocyanate of formula XIV following a method analogous to that of process 
(C) described hereinabove. 
The compounds of formula IX and XIV may be prepared respectively by 
reacting a compound of formula XVI or XVII, or a protected derivative 
thereof, with oxalyl chloride. The reaction is conveniently effected at a 
temperature in the range of from -10.degree. to 100.degree. C. Suitable 
solvents include halogenated hydrocarbons such as dichloromethane and 
nitriles such as acetonitrile. 
The compounds of formula XI in which R.sup.2 and R.sup.3 are hydrogen may 
be prepared by a method analogous to process (C), by reacting an amine of 
formula X with an isocyanate of formula XVIII, or a protected derivative 
thereof, followed if necessary by the removal of the protecting group(s). 
The compounds of formula XIII in which U.sup.2 is a (1-4C)alkylthio group 
may be prepared by reacting a compound of formula XIX with an alkylating 
agent, for example a (1-4C)alkyl halide such as methyl iodide. Suitable 
media for the reaction include ketones such as acetone. Conveniently the 
reaction may be performed at a temperature in the range of from 0.degree. 
to 100.degree. C. 
The compounds of formula XIX may be prepared by reacting a compound of 
formula XX with hydrogen sulphide. The reaction is conveniently effected 
in the presence of a base such as triethylamine and in the presence of a 
solvent such as pyridine. 
The compounds of formula XX may be prepared by reacting an amine of formula 
XXI with an isocyanate of formula IX. Suitable solvents for the reaction 
include nitriles such as acetonitrile. 
The compounds of formula XVIII may be prepared by reacting a compound of 
formula XXII, or a protected derivative thereof, with oxalyl chloride. 
Suitable solvents include halogenated hydrocarbons such as 
1,2-dichloroethane. 
The compounds of formula I may be converted into pharmaceutically 
acceptable salts and/or metabolically labile esters or amides thereof by 
methods well known in the art. For example, a pharmaceutically acceptable 
salt may be formed by reacting a compound of formula I with an acid 
capable of affording a physiologically acceptable anion, or a base capable 
of affording a physiologically acceptable cation. A pharmaceutically 
acceptable metabolically labile ester or amide may be formed respectively 
by esterifying a compound of formula I using a conventional technique, or 
by reacting an acid, or a reactive derivative thereof, with an appropriate 
amine. Similarly, when an optically active form of a chiral compound of 
formula I is required, either one of processes (A)-(E) above may be 
carried out using the appropriate optically active starting material or 
else a racemic form may be resolved by a conventional procedure, for 
example, using an optically active form of a suitable acid. 
A suitable reactive derivative of an acid may be, for example, an acyl 
halide, for example an acyl chloride formed by the reaction of the acid 
and an inorganic acid chloride, for example thionyl chloride; a mixed 
anhydride, for example an anhydride formed by the reaction of the acid and 
a chloroformate such as isobutyl chloroformate; an active ester, for 
example an ester formed by the reaction of the acid and a phenol such as 
pentafluorophenol or an alcohol such as 1-hydroxybenzotriazole; an acyl 
azide, for example an azide formed by the reaction of the acid and an 
azide such as diphenylphosphoryl azide; an acyl cyanide, for example a 
cyanide formed by the reaction of an acid and a cyanide such as 
diethylphosphoryl cyanide; or the product of the reaction of the acid and 
a carbodiimide such as dicyclohexylcarbodiimide. 
Many of the intermediates, for example compounds of formulae VI, VII, VIII, 
XI, XIII, XIX and XX are novel and form further aspects of this invention. 
The ability of the compounds of formula I to inhibit platelet aggregation 
may be demonstrated using a standard test (a) based on that described by 
Born (Nature, 1962, 194, 927-929) and involving: 
(i) aggregating human, citrated, platelet-rich plasma by addition of 
adenosine diphosphate (ADP) so as to generate a dose-response curve; 
(ii) generating a dose-response curve for ADP stimulated platelet 
aggregation in the presence of increasing amounts of a test compound 
(generally in the range 10.sup.-5 M to 10.sup.-10 M); and 
(iii) calculating a pA.sub.2 value indicating potency of platelet 
aggregation inhibition for the test compound, averaged over several 
concentrations, from the calculated 50% response value for ADP aggregation 
in the presence and absence of the test compound. 
Test (a) may be modified so as to assess the effects of a test compound ex 
vivo on the aggregation of human blood platelets after administration of 
the test compound to a laboratory animal, such as a rat, rabbit, guinea 
pig, mouse or dog. For example, groups of four male, fasted Alderley Park 
Wistar rats are orally dosed with a test compound or appropriate vehicle, 
and at suitable time intervals (1, 3, 5 and 8 hours after dosing) animals 
are anaesthetised with fluothane and bled by heart puncture. Blood is 
collected into 3.2% citrate (1 part to 9 parts whole blood) and platelet 
poor plasma (ppp) prepared by centrifugation (4500.times.g for 10 
minutes). 
Human blood is collected into 3.2% trisodium citrate (1 part to 9 parts 
whole blood) and centrifugated (200.times.g for 15 minutes) to produce 
platelet rich plasma (prp). 
Equal volumes (125 .mu.l) of rat ppp and human prp are mixed together, ADP 
added, and the whole incubated (37.degree. C.) and stirred (900 rpm) in a 
BioData platelet aggregometer. Aggregation is induced with ADP and agonist 
EC.sub.50 values calculated for human prp/rat ppp mixtures from animals 
dosed with test compound or vehicle. A mean concentration ratio 
(concentration of ADP required to cause a 50% aggregation response in 
human prp/rat ppp mixtures from animals dosed with antagonist, divided by 
the concentration of ADP to cause 50% aggregation in human prp/rat ppp 
mixtures from animals dosed with vehicle) is calculated at each time 
point. 
The ability of the compounds of formula I to inhibit binding of fibrinogen 
to GPIIb-IIIa may be demonstrated using the following standard test (b) 
involving: 
(i) Preparation of human platelet lysates. 
Platelet rich plasma (prp) is harvested by centrifugation (1000 rpm, 15 
minutes) of whole blood anticoagulated with acid citrate dextrose 
(trisodium citrate 85 mM, citric acid 70 mM, d-glucose 110 mM) 1 part to 6 
parts blood. Prostacyclin (PGI.sub.2, 1 .mu.M) is added to the prp before 
centrifugation (2400 rpm, 15 min) and the resulting pellet is resuspended 
in modified Tyrodes' solution (NaCl 130 mM, KCl 26 mM, NaHCO.sub.3 12 mM, 
NaH.sub.2 PO.sub.4 0.5 mM, MgCl.sub.2 1 mM, CaCl.sub.2 20 mM, Glucose 12 
mM, HEPES 5 mM) containing bovine serum albumin 3.5 g/L, PGI.sub.2 1 .mu.M 
and hirudin 0.5U/ml. The platelet suspension is centrifuged (2400 rpm, 15 
minutes) and the resultant pellet resuspended in 500 .mu.l of lysis buffer 
(octyl glucoside 50 mM, HEPES 10 mM, NaCl 150 mM, CaCl.sub.2 1 mM, 
MgCl.sub.2 1 mM, PMSF 1 mM, NEM 10 mM, leupeptin 0.1 mM), agitated at 
4.degree. C. for 15 minutes then centrifuged at 24000 rpm, 15 minutes. The 
supernatant is stored at 4.degree. C. and the pellet re-suspended in 500 
.mu.l of lysis buffer. The centrifugation process is repeated a further 3 
times, the pooled supernatants being stored at -70.degree. C. 
(ii) Receptor purification. 
Glycoprotein IIb/IIIa is isolated from human platelet lysates using a 2 ml 
peptide (KYGRGDS) coupled CNBr activated Sepharose affinity column. A 1.5 
ml volume of platelet lysate is placed on the column and allowed to stand 
overnight at 4.degree. C. Buffer (30 ml, octyl glucoside 25 mM, HEPES 10 
mM, NaCl 150 mM, CaCl.sub.2 1 mM, MgCl.sub.2 1 mM, PMSF 1 mM, NEM 10 mM, 
leupeptin 0.1 mM) is passed through the column and 2 ml fractions are 
collected throughout. GPIIb/IIIa is eluted with 12 ml of buffer containing 
HHLGGAKQAGDV (2 mg/ml, pH7.5), the column is washed using 4 ml buffer and 
the remaining GPIIb/IIIa eluted using 12 ml buffer containing GRGDSPG (1 
mg/ml pH7.5). The column is finally washed using 20 ml of buffer and can 
be used for up to three such preparations. Fractions containing GPIIb/IIIa 
are identified using gel electrophoresis and immunoblotting, pooled and 
stored at -70.degree. C. 
(iii) GPIIb/IIIa ELISA 
96 well microtitre plates are coated with 100 .mu.l purified human platelet 
fibrinogen receptor (GPIIb/IIIa) diluted in coating buffer (Tris-HCl 20 
mM, NaCl 150 mM, CaCl.sub.2 1 mM, pH7.4) and left overnight at 4.degree. 
C. The plates are washed using washing buffer (Tris-HCl 50 mM, NaCl 100 
mM, CaCl.sub.2 2 mM, pH7.4) and non-specific binding blocked by the 
addition of 200 .mu.l 2% BSA (2 hours, 30.degree. C.). The plates are 
washed prior to incubation (2 hours, 30.degree. C.) with 100 .mu.l 
biotinylated fibrinogen (10 nM) containing either vehicle or test 
compound. The plates are washed, incubated with streptavidin (5 .mu.g/ml, 
1 hour, ambient temperature), then washed again before the addition of 100 
.mu.l biotinylated horse radish peroxidase (0.1 .mu.g/ml, 1 hour, ambient 
temperature). The plates are then washed and equal volumes of peroxidase 
substrate (3,3',5,5'-tetramethylbenzidine 0.4 g/l) and H.sub.2 O.sub.2 
(0.02%) are mixed together immediately before addition of 150 .mu.l to 
each well. Colour is allowed to develop for 10-15 minutes before optical 
densities are read at 650 nm. 
Abbreviations 
PMSF Phenylmethylsulphonyl fluoride 
HEPES 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulphonic acid 
NEM N-ethylmaleimide 
The concentration of compound required to cause 50% inhibition of 
biotinylated fibrinogen binding is calculated and expressed as a 
pIC.sub.50 (-log (IC.sub.50)). 
The compounds of formula I exemplified herein have been found to show 
effects in the following ranges in at least one of the above tests: 
test (a): pA.sub.2 of&gt;4.5 
test (b): pIC.sub.50 of&gt;4.5 
In general, it has been found that compounds of formula I in which G is 
carboxy show a higher level of activity in test (a) and test (b) than 
those in which G is an ester group. 
For example, the compound described in Example 1 hereinafter has been found 
to give a pA.sub.2 of 7.5 in test (a) and a pIC.sub.50 of 6.9 in test (b), 
whereas the compound of Example 2 has been found to give a pA.sub.2 of 7.6 
in test (a) and a pIC.sub.50 of 7.6 in test (b). 
As stated previously, the compounds of formula I may be used in the therapy 
or prevention of diseases in which cell adhesion (especially platelet 
aggregation) is involved, for example venous or arterial thrombosis (for 
example pulmonary embolism, stroke and thrombotic events accompanying 
unstable angina and transient ischaemic attack), myocardial infarction, 
migraine, atherosclerosis, thromboembolism and reocclusion during and 
after thrombolytic therapy. The compounds may also be useful for the 
prevention of reocclusion or restenosis following percutaneous 
transluminal coronary angioplasty (PTCA) and coronary artery bypass graft. 
It will also be appreciated that the compounds may be useful in the 
treatment of other diseases mediated by binding of adhesion molecules to 
GPIIb/IIIa, for example cancer. 
According to another aspect, therefore, the invention provides a method of 
inhibiting platelet aggregation in a warm-blooded mammal requiring such 
treatment, which comprises administering an effective amount of a compound 
of formula I, or a pharmaceutically acceptable metabolically labile ester 
or amide thereof, or a pharmaceutically acceptable salt thereof. 
According to yet another aspect, the invention provides a method of 
inhibiting binding of fibrinogen to GPIIb/IIIa in a warm-blooded animal 
requiring such treatment, which comprises administering an effective 
amount of a compound of formula I, or a pharmaceutically acceptable 
metabolically labile ester or amide thereof, or a pharmaceutically 
acceptable salt thereof. 
According to a further aspect, the invention provides the use of a compound 
of formula I, or a pharmaceutically acceptable metabolically labile ester 
or amide thereof, or a pharmaceutically acceptable salt thereof, for the 
manufacture of a medicament for the prevention or treatment of a disease 
involving platelet aggregation. 
According to yet another aspect, the invention provides the use of a 
compound of formula I, or a pharmaceutically acceptable metabolically 
labile ester or amide thereof, or a pharmaceutically acceptable salt 
thereof, for the manufacture of a medicament for the prevention or 
treatment of a disease involving binding of fibrinogen to GPIIb/IIIa. 
In general, a compound of formula I will be administered for this purpose 
by an oral, rectal, topical, intravenous, subcutaneous, intramuscular or 
inhalation route, so that a dose in the range of from 0.01 to 50 mg/kg 
body weight will be given, depending upon the route of administration, the 
age and sex of the patient, and the severity of the condition to be 
treated. 
The compounds of formula I will generally be used in the form of a 
pharmaceutical composition comprising a compound of formula I, or a 
pharmaceutically acceptable metabolically labile ester or amide thereof, 
or a pharmaceutically acceptable salt thereof, together with a 
pharmaceutically acceptable diluent or carrier. Such a composition is 
provided as a further feature of the invention and may be in a variety of 
dosage forms. For example, it may be in the form of tablets, capsules, 
solutions or suspensions for oral administration; in the form of creams or 
ointments or a transdermal (skin) patch for topical administration; in the 
form of a suppository for rectal administration; in the form of a sterile 
solution or suspension for administration by intravenous or intramuscular 
injection; in the form of an aerosol or a nebuliser solution or 
suspension, for administration by inhalation; and in the form of a powder, 
together with pharmaceutically acceptable inert solid diluents such as 
lactose, for administration by insufflation. Depending upon the route of 
administration, the composition will, in general, comprise, for example, 1 
to 99% by weight of a compound of formula I. 
The pharmaceutical compositions may be obtained by conventional procedures 
using pharmaceutically acceptable diluents and carriers well known in the 
art. Tablets and capsules for oral administration may conveniently be 
formed with an enteric coating, for example comprising cellulose acetate 
phthalate, to minimise contact of the active ingredient of formula I with 
stomach acids. 
The compounds according to the invention may be co-adminstrated or 
co-formulated with one or more agents known to be of value in diseases or 
conditions intended to be treated; for example a known platelet 
aggregation inhibitor (e.g. aspirin, a thromboxane antagonist or a 
thromboxane synthase inhibitor), hypolipidemic agent, anti-hypertensive 
agent, thrombolytic agent (such as streptokinase, urokinase, prourokinase, 
tissue plasminogen activator and derivatives thereof), beta-adrenergic 
blocker or a vasodilator may usefully also be present in a pharmaceutical 
composition of the invention for use in treating a heart or vascular 
disease or condition. 
In addition to their use in therapeutic medicine, the compounds of formula 
I are also useful as pharmacological tools in the development and 
standardisation of test systems for the evaluation of the effects of 
adhesion molecules in laboratory animals such as cats, dogs, rabbits, 
monkeys, rats and mice, as part of the search for new therapeutic agents. 
The compounds of formula I may also be used because of their platelet 
aggregation inhibitory properties in helping to store blood and to 
maintain the viability of blood and blood vessels in warm-blooded animals 
(or parts thereof) under-going artificial extracorporeal circulation, for 
example during limb or organ transplants. When used for this purpose a 
compound of formula I, or a pharmaceutically acceptable salt thereof, will 
generally be administered so that a steady state concentration in the 
range, for example, 0.1 to 10 mg per liter is achieved in the blood. 
The invention will now be illustrated by the following non-limiting 
Examples in which unless otherwise stated: 
(i) concentrations and evaporations were carried out by rotary evaporation 
in vacuo; 
(ii) operations were carried out at ambient temperature, that is, in the 
range 18.degree.-26.degree. C.; 
(iii) column chromatography was carried out on silica (Merck Art. 9385) 
available from E Merck and Co., Darmstadt, Germany; 
(iv) yields are given for illustration only and are not necessarily the 
maximum attainable by diligent process development; 
(v) proton NMR spectra were normally determined at 200 MHz or 250 MHz in 
dimethylsulphoxide-d.sub.6 using tetramethylsilane (TMS) as an internal 
standard, and are expressed as chemical shifts (delta values) in parts per 
million relative to TMS using conventional abbreviations for designation 
of major peaks: s, singlet; m, multiplet; t, triplet; br, broad; d, 
doublet; and 
(vi) ether refers to diethyl ether, DMSO to dimethylsulphoxide and TFA to 
trifluoroacetic acid.