, ???NHS(O)2R2, ???OC2-C4alkyl???C(O)OR2, ???C(O)R2 and carboxylic acid analogs, wherein R2 is a member selected from the group consisting of hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C3-C8 cycloalkyl, substituted or unsubstituted heterocyclyl; substituted or unsubstituted aryl and substituted or unsubstituted aryl C1-C4 alkyl.