Patent ID: 7803810

Claim:
A compound of formula (I), or a pharmaceutically acceptable salt thereof, wherein: R 1 represents C 2-8 alkyl; C 2-8 alkenyl; —(C 1-6 alkyl)-aryl; —(C 1-6 alkyl)-heteroaryl; —(C 1-6 alkyl) -carbocyclyl; —(C 1-6 alkyl)-heterocyclyl; -aryl; -heteroaryl; -carbocyclyl or -heterocyclyl; wherein said aryl or heteroaryl groups may be optionally substituted by one or more substituents selected from, C 1-4 alkyl, C 1-4 fluoroalkyl, C 1-4 alkoxy, C 1-4 fluoroalkoxy, hydroxy, —SO 2 (C 1-4 alkyl), —SO 2 N(C 1-4 alkyl)(C 1-4 alkyl), SOC 1-4 alkyl, —SOC 3-6 cycloalkyl, —C(O)O(C 1-4 alkyl), benzyloxy and phenyl; and wherein said carbocyclyl and heterocyclyl groups may be optionally substituted by one or more substituents selected from —C 1-4 alkyl, —C 1-4 alkoxy, hydroxyl, halogen and oxo; R 2 represents H; C 1-4 alkyl or halogen; R 3 represents H; C 1-4 alkyl or halogen; and R 4 represents H; C 1-4 alkyl or halogen.