Synthesis of conformationally constrained cyclic peptides using an intramolecular Sonogashira coupling

Abstract

Small peptides having a 3-bromobenzyl group at the C-termini and n-alkynoyl group at the N-termini undergo a smooth copper-free intramolecular Sonogashira coupling reaction to afford the corresponding cyclic peptides in moderate yields. Scope and limitations of this macrocyclization is demonstrated with di-, tri-, and tetrapeptides. © 2005 American Chemical Society.