| abstract |
A compound of the formula (I):n or a pharmaceutically acceptable salt thereof, wherein:n R 1 is a hydrogen atom, a substituted or unsubstituted C 1-6 alkyl group, a C 2 - 6 alkenyl group, a C 2 - 6 alkynyl group or a R 7- CO- group (wherein R 7 is a C 1-6 alkyl group, a phenyl group, a C 2-6 alkenyl group which may be substituted by a phenyl group, or a C 1-6 alkoxy group); R 2 is a hydrogen atom, a substituted or unsubstituted C 1 - 8 alkyl group, or a phenyl group; R 3 is a hydrogen atom, and R 4 is a hydroxyl group, or R 3 and R 4 together form a bond; each of R 5 and R 6 is a C 1 - 4 alkyl group; and Y is a cyano group, a halogen atom, a nitro group, a C 1-6 alkyl group, a C 2 - 6 alkynyl group, a C 1-6 alkylcarbonyl group, a C 1-6 alkoxy group, a di-C 1-6 alkylaminocarbonyl group, an aryl group, a C 1-6 alkoxycarbonyl group, a carboxyl group or a morpholinocarbonyl group. |