Sidechain‐Backbone Tetrel Bonding Interactions Provide a General Mechanism for trans‐Peptoid Stabilization

Abstract

AbstractCis‐trans isomerization of amide bonds impedes de novo design of folded peptoids (poly‐N‐substituted glycines) with precise secondary structures and affects peptoid‐biomolecule binding affinity. Herein, from X‐ray, NMR and DFT studies of azapeptoids, we have discovered a tetrel bonding interaction that stabilizes trans‐peptoids. We show that peptoids having α‐heteroatoms and N‐aryl groups in the sidechain adopt trans‐amide geometries due to the presence of a nX/πAr→σ*Cα−N tetrel bonding interaction between the sidechain α‐heteroatom lone pair (nX) or π‐electrons (πAr) and the σ* orbital of the backbone Cα−N bond. Further, CD spectroscopic studies of oligo‐proline host–guest model peptides showed that azapeptoid residues stabilize polyproline II helical conformation. These data indicate that the sidechain‐backbone tetrel bonding could be leveraged to design peptoids with precise secondary structures for a wide range of biological and material applications.