Zn-Catalyzed Nicotinate-Directed Transamidations in Peptide Synthesis
Charlie Hollanders, Evelien Renders, Charlène Gadais, Dario Masullo, Laurent Van Raemdonck, Clarence C. D. Wybon, Charlotte Martin, Wouter Herrebout, Bert U. W. Maes, Steven Ballet
Abstract
A chemoselective and catalytic transamidation for peptide synthesis is described. Transamidation under Zn catalysis is chemoselectively achieved by amino acid amide/peptidic amide derivatization with a tert-butyl nicotinate (tBu-nic) directing group. The directing group could be easily introduced on protected amino acid amides via Pd-catalyzed amidation with tert-butyl 2-chloronicotinate (tBu-nicCl). Under standard peptide coupling/deprotection conditions, the tBu-nic-equipped amino acid amides proved to be fully inert, allowing them to be easily built-in in complex molecules. The disclosed method was evaluated in the synthesis of diverse dipeptides, in dipeptide segment coupling, in side-chain modification of a solid-supported tetra-/pentapeptide, and in the macrocyclization of a heptapeptide.