Non‐classical Helices with cis Carbon–Carbon Double Bonds in the Backbone: Structural Features of α,γ‐Hybrid Peptide Foldamers

Abstract

The impact of geometrically constrained cis α,β‐unsaturated γ‐amino acids on the folding of α,γ‐hybrid peptides was investigated. Structure analysis in single crystals and in solution revealed that the cis carbon–carbon double bonds can be accommodated into the 12‐helix without deviation from the overall helical conformation. The helical structures are stabilized by 4→1 hydrogen bonding in a similar manner to the 12‐helices of β‐peptides and the 310 helices of α‐peptides. These results show that functional cis carbon–carbon double bonds can be accommodated into the backbone of helical peptides.