Synthesis of lactam-bridged cyclic peptides using sequential olefin metathesis and diimide reduction reactions

A new approach has been developed for the synthesis of lactam-bridged cyclic peptides. Following the introduction of N-allyl glutamine and α-allylglycine into the peptide backbone, the side chains of these residues were subjected to a cyclization reaction by ring-closing metathesis (RCM). Reduction of the resulting peptide bearing olefin moiety was achieved using diimide, which was generated in situ from o-nitrobenzenesulfonyl hydrazine and piperidine, gave the corresponding saturated cyclic peptides.