Patent ID: 8232427

Claim:
A compound of formula (I) wherein R 1 is cyano, (C 1 -C 7 )alkyl, R 4 —O—, (C 1 -C 7 )alkyl-NHC(O)—, R 6 C(O)—, or R 9 —C(O)—O—, wherein R 4 , R 6 , and R 9 are independently hydrogen, (C 1 -C 7 )alkyl, mono- or di-(C 1 -C 7 )alkylamino or aryl each of which is optionally substituted by one to five substituents selected from the group consisting of (C 1 -C 7 )alkyl, halo, hydroxyl, (C 1 -C 7 )alkoxy and aryl; R 2 is (C 1 -C 7 )alkyl which is optionally substituted by one to three substituents selected from the group consisting of (C 1 -C 7 )alkyl, hydroxy, aryl, heterocyclyl, heteroaryl, (C 1 -C 7 )alkyl-O—C(O)—, di-(C 1 -C 7 )alkylamino-C(O)—, wherein each of aryl, heterocyclyl, and heteroaryl is further optionally substituted by (C 1 -C 7 )alkyl; or R 3 is (C 1 -C 7 )alkyl, or cycloalkyl; a pharmaceutically acceptable salt thereof; or an optical isomer thereof; or a mixture of optical isomers.