Patent ID: 7304046

Claim:
A compound a compound of formula I: wherein: R 1 is an organic releasing group comprising a quinone ring; R a , R b , R c , and R d are each independently hydrogen, (C 1 –C 6 )alkyl, or —CH 2 CH 2 X; and each X is independently halo, (C 1 –C 6 )alkylsulfonyl, halo(C 1 –C 6 )alkylsulfonyl, or arylsulfonyl, wherein each aryl is optionally substituted with one or more (e.g. 1, 2, 3, or 4) halo, (C 1 –C 6 )alkyl, halo(C 1 –C 6 )alkyl, (C 1 –C 6 )alkoxy, (C 1 –C 6 )alkanoyl, (C 1 –C 6 )alkanoyloxy, (C 1 –C 6 )alkoxycarbonyl, cyano, nitro, or trifluoromethoxy; provided at least two of R a , R b , R c , and R d are —CH 2 CH 2 X; or a pharmaceutically acceptable salt thereof.