Traceless Ligation of Cysteine Peptides Using Selective Deselenization

Selective deselenization: Native chemical ligation at selenocysteine is followed by selective deselenization of the selenocysteine to alanine, in the presence of cysteine residues without protecting groups (see scheme). This selectivity is achieved by using the water-soluble tris(2-carboxyethyl)phosphine (TCEP) in the absence of a radical initiator.