Patent ID: 7767853

Claim:
A compound represented by Structural Formula I: wherein: R and R′ are independently H or optionally substituted alkyl and at least one of R and R′ is H; Z is —C(O)NR c —, —NR c C(O)—, —NR c —, —CR c ═N—, —C(O)—, —C(O)O—, —OC(O)—, —O—, —S—, —C(O)OC(O)— or a bond; R c is independently H or optionally substituted alkyl; R a , for each occurrence, is independently an optionally substituted alkyl, optionally substituted aryl, optionally substituted alkoxycarbonyl, optionally substituted ester, —OH, —NH 2 , —SH; R b , for each occurrence, is independently H or optionally substituted alkyl; s, for each occurrence, is independently integers from 0 to 4; and m and n, for each occurrence, are independently integers from 0 to 6.