Patent ID: 8222440

Claim:
A compound having a structure of formula (I) or a pharmaceutically acceptable salt thereof wherein X is S or Se; W is O, S, or (R)(R), where each occurrence of R is independently H or a C 1-2 alkyl; n is an integer from 9 to 20; R 1 and R 2 are independently C 1-10 alkyl; R 3 is —H, C 1-10 alkyl, or C 0-6 alkyl-COOR 6 ; R 3′ is H, amino, cyano, halogen, aryl, aralkyl, heteroaryl, heteroaralkyl, carboxyl, C 1-10 alkyl, C 1-10 alkenyl, or C 1-10 alkynyl; R 4 is —OH, —H, —CH 3 , amino, —OC(O)C 1-10 aralkyl, —OC(O)C 1-10 alkyl, —OC(O)aryl, or a glutamine substituent; R 5 is —OH, cyano, C 1-10 alkoxy, amino, O-aralkyl, —OC(O)C 1-10 aralkyl, —OC(O)C 1-10 alkyl, —OC(O)aryl, or a glycine substituent; and R 6 is H or C 1-10 alkyl.