Study of chemical ligation via 17-, 18- and 19-membered cyclic transition states.

ABSTRACT

Unprotected S-acylated cysteine isopeptides containing α-, ß- or γ-amino acid units have been synthesized, and their conversion to native hexapeptides by S- to the N-terminus ligations involving 17-, 18- and 19-membered cyclic transition states have been demonstrated both experimentally and computationally to be more favorable than intermolecular cross-ligations.