Patent ID: 7332623

Claim:
A compound of formula (I): or a pharmaceutically acceptable salt thereof, wherein R 1 =R 2 =H; or R 1 and R 2 together form a moiety represented by the formula R 3 represents a substituted alkyl having 4-30 carbon atoms, wherein the alkyl group is substituted with one to three substituents selected from the group consisting of halo, cyano, amino, nitro, carbonyl, carboxyl, hydroxy, C 1 -C 6 alkyl, C 1 -C 6 hydroxyalkyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 alkylthio, C 1 -C 6 alkanoyl, and C 1 -C 6 alkanoyloxy, a substituted aryl group having 3-30 carbon atoms, wherein the aryl group is substituted with one to three substituents selected from the group consisting of halo, cyano, amino, nitro, carbonyl, carboxyl, hydroxy, hydroxycarbonyl, C 1 -C 6 alkyl, C 1 -C 6 hydroxyalkyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 alkylthio, C 1 -C 6 alkanoyl, C 1 -C 6 alkanoyloxy, t-butyldimethylsilyloxy, and phenyl tetrahydropyranyloxyalkyl, or (C 5 -C 8 aryl)oxyalkyl; and R 4 represents (A) a substituted or unsubstituted aryl group having 3-30 carbon atoms, wherein the aryl group is optionally substituted with one to three substituents selected from the group consisting of halo, cyano, amino, nitro, carbonyl, carboxyl, hydroxy, hydroxycarbonyl, C 1 -C 6 alkyl, C 1 -C 6 hydroxyalkyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 alkylthio, C 1 -C 6 alkanoyl, C 1 -C 6 alkanoyloxy, t-butyldimethylsilyloxy, and phenyl; or (B) (C 5 -C 8 aryl)oxyalkyl, tetrahydropyranyloxyalkyl; (C) a substituted phenylene or biphenylene group represented as where n is 1 or 2.