Site-Selective Modification of Peptides: From Customizable Units to Novel α-Aryl and α-Alkyl Glycine Derivatives, and Components of Branched Peptides

The creation of peptide libraries by site-selective modification of a few peptide substrates would increase the efficiency of discovery processes, but still is a real synthetic challenge. The site-selective modification of small peptides at serine or threonine residues, by using a short scission-addition procedure, allows the preparation of peptides with unnatural alpha-aryl glycines. In a similar way, the scission of hydroxyproline residues is the key step in the production of optically pure alpha-alkyl glycines which are precursors or components of branched peptides. With these versatile processes, a single peptide can be transformed into a variety of peptide derivatives. The process takes place under mild conditions, and good global yields are obtained. (C) 2015 Wiley Periodicals, Inc.