Site-specific C-functionalization of free-(NH) peptides and glycine derivatives via direct C–H bond functionalization

A copper-catalyzed alpha-functionalization of glycine derivatives and short peptides with nucleophiles is described. The present method provides ways to introduce functionalities such as aryl, vinyl, alkynyl, or indolyl specifically to the terminal glycine moieties of small peptides, which are normally difficult in peptide modifications. Furthermore, on functionalization, the configurations of other stereocenters in the peptides could be maintained. Because the functionalized peptides could easily be deprotected and carried onto the next coupling process, our approach provides a useful tool for the peptide-based biological research.