Patent ID: 8455688

Claim:
A compound having the structure wherein n is 1-10; X is C—R 11 or N, wherein R 11 is H, OH, SH, F, Cl, SO 2 R 7 , NO 2 , trifluoromethyl, methoxy, or CO—R 7 , wherein R 7 is alkyl, alkenyl, alkynyl, C 3 -C 8 cycloalkyl, or aryl; R 2 is H or NR 3 R 4 , wherein R 3 and R 4 are each independently H or C 2 -C 6 alkyl; R 5 is SH; and R 6 , R 12 , R 13 , and R 14 are each independently H, OH, SH, F, Cl, SO 2 R 15 , NO 2 , trifluoromethyl, methoxy, or CO—R 15 , wherein R 15 is alkyl, alkenyl, alkynyl, C 3 -C 8 cycloalkyl, or aryl, or a salt of the compound.