Patent ID: 8153657

Claim:
A compound represented by formula I: wherein R 1 represents independently for each occurrence H or alkyl; R 2 is H, alkyl, aryl, aralkyl, or —C(O)R 5 ; R 3 is aryl optionally substituted, heteroaryl, or aralkyl; R 4 is C(O)N(R 6 ) 2 ; R 5 is alkyl, aryl, heteroaryl, or aralkyl; R 6 represents independently for each occurrence hydrogen, alkyl, aryl, or aralkyl, wherein any two instances of R 6 may be covalently attached to form a ring; X is S, —S(O)—, or —S(O 2 )—; n is 1, 2, 3, or 4; and m is 1, 2, 3, or 4.