Patent ID: 8329658

Claim:
A compound of formula (I): wherein: A is (E)-CH═CHCH 2 R or —CH 2 CH 2 CH 2 R, wherein R represents hydrogen, —SH, thioalkyl, carboxyl or alkoxycarbonyl; B is ethyl, 1-hydroxyethyl, isopropyl or n-propyl; R 1 is —Y—Ar; R 2 is isobutyl or 2-hydroxyisobutyl; X is —S(O) n — or oxygen; Y is straight- or branched-C 1-6 alkylene, C 2-6 alkenylene or C 2-6 alkynylene; Ar is: a heterocyclic ring optionally substituted by one or more groups R 3 which may be the same or different, wherein said heterocyclic ring is attached to the group Y via a ring carbon atom and wherein the heterocyclic ring is an aromatic heterocyclic group having 5 or 6 atoms, up to three of which are selected from oxygen, nitrogen and sulfur; R 3 is selected from the group consisting of halogen, hydroxy, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 haloalkyl, C 1-6 haloalkoxy, carboxyl, alkoxycarbonyl, —NR 4 R 5 and —NR 6 (CH 2 ) m NR 4 R 5 ; R 4 and R 5 , which may be the same or different, is: hydrogen; straight- or branched-chain alkyl comprising from one to six carbon atoms, optionally substituted by one or more halogen; straight- or branched-chain alkenyl or alkynyl comprising from two to four carbon atoms; cycloalkyl containing from three to six carbon atoms optionally substituted by straight- or branched-chain alkyl containing from one to six carbon atoms; or R 4 and R 5 , together with the nitrogen atom to which they are attached, form a saturated or unsaturated heterocyclic ring containing from four to six ring atoms, which ring may optionally contain another heteroatom selected from the group consisting of nitrogen, oxygen and sulfur and may be optionally substituted by from one to four groups which may be the same or different selected from the group consisting of alkyl, phenyl and benzyl; R 6 is hydrogen or straight- or branched-chain alkyl containing from one to six carbon atoms; n is zero, one or two; m is an integer from two to four; or a pharmaceutically acceptable salt thereof.