Rǒle des electrons π des fonctions amide et ester dans les peptides et depsipeptides

✍ Scribed by G. Boussard; M. Marraud

• Publisher: Wiley (John Wiley & Sons)
• Year: 1981
• Tongue: English
• Weight: 975 KB
• Volume: 20
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1981.360200112

✦ Synopsis

Abstract

The IR data for the R^1^ CO‐O‐CHR^2^‐CO‐NHR^3^ derivatives are interpreted in terms of a H…π interaction involving the NH bond and the π orbitals of the ester function and giving rise to a high ν(CO) frequency and a low ν frequency. The resulting molecular conformation corresponds to the angular values ϕ # −90°, ψ # 0°. The H…π interaction in MeCO‐L‐Lac‐NHMe is highly destabilized by water and aprotic solvents but is retained in methanol. Considering the high ν(CO) ester or amide frequency of the middle function in β‐folded depsipeptide or peptide sequences, it may be supposed that the residue indexed i + 2 in β turns experiences a H…π interaction which has a stabilizing effect on β turns. Some examples concerning valinomycin and some model compounds are discussed.