Patent ID: 8748435

Claim:
A compound of formula (I) or a pharmaceutically acceptable salt thereof, wherein R1 is H or C 1 -C 6 alkyl; R2 and R3 are independently from each other H or C 1 -C 6 alkyl; A is a bivalent linking group selected from the group consisting of: —CH═CH—, —CH═CH—CH 2 —,—CH 2 —CH═CH—, —CH 2 —CH 2 —CH 2 —, —CH═CH—C(O)—, —C(O)—CH═CH—, —CH 2 —CH 2 —C(O)—, —C(O)—CH 2 —CH 2 —, —C(O)—NH—CH 2 —, —CH 2 —NH—C(O)—, —O—CH 2 —, —CH 2 —O—, —O—CH 2 —CH 2 —, —CH 2 —CH 2 —O—, (wherein a* denote the link (or places of attachment)); R stands for heterocyclyl or cycloalkyl, each of which may be optionally substituted 1 to 4 times; and R4 is H, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, halogen, hydroxy, cyano or trifluoromethyl.