Peptide ligation chemistry at selenol amino acids

The convergent assembly of peptide fragments by native chemical ligation has revolutionized the way in which proteins can be accessed by chemical synthesis. A variation of native chemical ligation involves the reaction of peptides bearing an N-terminal selenocysteine residue with peptide thioesters, which proceeds through the same mechanism as the parent reaction. This transformation was first investigated in 2001 for the installation of selenocysteine into peptides and proteins via ligation chemistry. The recent discovery that selenocysteine residues within peptides can be chemoselectively deselenized without the concomitant desulfurization of cysteine residues has led to renewed interest in ligation chemistry at selenocysteine. This review outlines the use of selenocysteine in ligation chemistry as well as recent investigations of chemoselective ligation-deselenization chemistry at other selenol-derived amino acids that have the potential to greatly expand the number of targets that can be accessed by chemical synthesis.