Efficient Construction of Proline-Containing β‑Turn Mimetic Cyclic Tetrapeptides via CuAAC Macrocyclization

A range of macrocyclic β-turn mimetic tetrapeptides was prepared by efficient copper-tris(triazole) ligand complex catalyzed azide–alkyne “click” macrocyclizations in good to high yields. Preliminary conformational studies using X-ray crystallography and NMR spectroscopy demonstrated the presence of intramolecular H-bonds characteristic of β-turns in these cyclic tetrapeptides.