Structures of peptides from α‐amino acids methylated at the α‐carbon,

Abstract The structural preferences of peptides (and depsipeptides) from the achiral MeAib and Hib residues, and the chiral Iva, (αMe) Val, (αMe) Leu, and (αMe) Phe residues, as determined by conformational energy computations, x‐ray diffraction analyses, and 1 H‐nmr and spectroscopic studies, are reviewed and compared with literature data on Aib‐containing peptides. The results obtained indicate that helical structures are preferentially adopted by peptides rich in these α‐amino acids methylated at the α‐carbon. Intriguing experimental findings on the impact of the chirality of Iva, (αMe) Val, and (αMe) Phe residues on helix screw sense are illustrated. © 1993 John Wiley & Sons, Inc.