Patent ID: 8513277

Claim:
A compound of the formula (I) or a pharmaceutically acceptable salt thereof: wherein: R 1 is hydrogen; a straight or branched C 1 -C 6 alkyl group, optionally substituted with one or more substituents selected from the group consisting of C 1 -C 5 alkoxy, hydroxy, C 3 -C 7 cycloalkyl, C 1 -C 3 alkyl-thiazolyl, and 1,3-dioxolanyl; a straight or branched C 2 -C 6 alkenyl group; a straight or branched C 2 -C 6 alkynyl group; a C 3 -C 7 cycloalkyl group; or a benzyl group, optionally substituted with one or more substituents selected from the group consisting of halogen, C 1 -C 3 alkyl, and C 1 -C 3 alkoxy, R 2 is a straight or branched C 1 -C 6 alkyl group, R 3 is hydrogen; a straight or branched C 1 -C 6 alkyl group; a straight or branched C 2 -C 6 alkenyl group; or a benzyl group optionally one or more substituted with halogen, and R 4 is an amino group substituted with one or two substituents selected from the group consisting of hydrogen, straight or branched C 1 -C 5 alkylcarbonyl, phenoxycarbonyl, benzyl optionally one or more substituted with halogen, and benzoyl optionally one or more substituted with halogen.