Site-selective modification of peptides: From "customizable units" to novel α-aryl and α-alkyl glycine derivatives, and components of branched peptides

ABSTRACT 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 α‐aryl glycines. In a similar way, the scission of hydroxyproline residues is the key step in the production of optically pure α‐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. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 104: 650–662, 2015.