| abstract |
A compound of ** formula ** in which R 1 is C 1-6 alkyl, optionally substituted with -OH, -C 1-4 alkyl or het; wherein C1-6 alkyl is optionally partially unsaturated; wherein het is a 5 or 6 membered heterocyclic ring radical having one or two heteroatoms selected from the group consisting of oxygen, sulfur and N; or a pharmaceutically acceptable salt, racemate, solvate, tautomer or optical isomer thereof. |