Native chemical ligation using removable Nα-(1-phenyl-2-mercaptoethyl) auxiliaries

A new methodology to extend native chemical ligation is presented. This method makes use of a novel 1-phenyl-2-mercaptoethyl auxiliary moiety on the α-amino group of a first peptide segment, the auxiliary acts as a 1-amino-2-thiol-containing functional group to effect thioester-mediated, amide-forming ligation with a second thioester-containing peptide. Subsequent facile removal of the auxiliary from the newly formed amide gives products with only native peptide structures.