Patent ID: 8168634

Claim:
A compound of formula (I), or a pharmaceutically acceptable salt thereof: wherein R 1 represents —COR a or —CONR b R c ; R a represents C 1-6 alkyl; R b represents hydrogen, C 1-6 alkyl, C 3-7 cycloalkyl or C 3-7 cycloalkyl(C 1-6 )alkyl; R c represents hydrogen or C 1-6 alkyl; R 2 represents hydrogen, C 1-6 alkyl, halogen, cyano or trifluoromethyl; R 3 represents C 1-6 alkyl, C 3-7 cycloalkyl, C 3-7 cycloalkyl(C 1-6 )alkyl, aryl, aryl(C 1-6 )alkyl, aryl(C 2-6 )alkenyl, aryl(C 2-6 )alkynyl, biaryl(C 1-6 )alkyl, C 3-7 heterocycloalkyl, C 3-7 heterocycloalkyl(C 1-6 )alkyl, C 3-7 heterocycloalkylcarbonyl, heteroaryl, heteroaryl(C 1-6 )alkyl, heteroaryl-aryl(C 1-6 )alkyl or aryl-heteroaryl(C 1-6 )alkyl, any of which groups may be optionally substituted by one or more substituents; and R 4 represents hydrogen; or C 1-6 alkyl, C 3-7 cycloalkyl, C 3-7 cycloalkyl(C 1-6 )alkyl, aryl, aryl(C 1-6 )alkyl, aryl(C 2-6 )alkenyl, aryl(C 2-6 )alkynyl, biaryl(C 1-6 )alkyl, C 3-7 heterocycloalkyl, C 3-7 heterocycloalkyl(C 1-6 )alkyl, C 3-7 heterocycloalkylcarbonyl, heteroaryl, heteroaryl(C 1-6 )alkyl, heteroaryl-aryl(C 1-6 )alkyl or aryl-heteroaryl(C 1-6 )alkyl, any of which groups may be optionally substituted by one or more substituents; or R 3 and R 4 , when both are attached to the same carbon atom, represent, when taken together with the carbon atom to which they are both attached, C 3-7 cycloalkyl or C 3-7 heterocycloalkyl, either of which groups may be optionally substituted by one or more substituents; or R 3 and R 4 , when attached to adjacent carbon atoms, represent, when taken together with the carbon atoms to which they are attached, C 5-7 cycloalkyl, phenyl, C 5-7 heterocycloalkyl or heteroaryl, any of which groups may be optionally benzo-fused and/or substituted by one or more substituents.