Patent ID: 7582642

Claim:
A compound of formula I or a pharmaceutically acceptable salt thereof, wherein one of R 1 and R 2 is methyl, ethyl or isopropyl, and the other is H; R 3 and R 4 are each independently H, branched C 3 -C 6 alkyl, or aryl, and wherein at least one of R 3 and R 4 is other than H; R 5 is a branched or unbranched C 1 -C 5 alkyl group or a C 3 -C 6 cycloalkyl group, each of which may be optionally substituted with one or more OH groups; R 6 , R 7 , R 8 and R 9 are each independently H, halogen, NO 2 , OH, OMethyl, CN, NH 2 , COOH, CONH 2 , or SO 2 NH 2 .