Patent ID: 8063249

Claim:
A compound of formula I or formula II: and pharmaceutically acceptable salts thereof, wherein X is H, O or S; R 1 is H, or if X is O, XR 1 is independently selected from the group consisting of alkyl esters, phosphate esters, diphosphate esters, and triphosphate esters, or not present when X is H; R 2 is H, CH 3 , a lower alkyl group, a divalent cyclic alkyl group forming a quaternary ammonium, an amide, a carbamate, an N-acyloxyalkyl group, an N-acylalkoxy carbonyl group, a beta-aminoketone, a (oxodioxolenyl)methyl group, an N-Mannich base, an imine (Schiff base), an enamine, an enaminone, an azo compound, THTT or PEG; R 3 is selected from a C 1 -C 6 perfluoroalkyl group; n is an integer from 1 to 10; and Y is a linker.