Patent ID: 8426444

Claim:
A compound having the structure wherein bond α is present or absent; R 1 and R 2 is each independently H, O − or OR 9 , where R 9 is H, alkyl, alkenyl, alkynyl or aryl, or R 1 and R 2 together are ═O; R 3 is OH, O − , OR 9 , SH, S − , or SR 9 ; R 4 is R 5 and R 6 is each independently H, OH, or R 5 and R 6 taken together are ═O; and R 7 and R 8 is each independently H, F, Cl, Br, SO 2 Ph, CO 2 CH 3 , or SR 12 , where R 12 is H, aryl or a substituted or unsubstituted alkyl, alkenyl or alkynyl, or a salt, enantiomer or zwitterion of the compound.