Stable Helical Secondary Structure in Short-Chain N,N′-Linked Oligoureas Bearing Proteinogenic Side Chains Access to both the Bruker ARX 500 facilities of the Service Commun de RMN (Faculté de Chimie, Strasbourg) and the Bruker DRX 600 NMR facilities of the Service Commun de Biophysicochimie des Interactions Moléculaires (Université Henri Poincaré, Nancy I) were deeply appreciated.

Abstract

Closely related to the (P)2.614 helix of γ-peptides: Heptamer 1 bearing side chains of Ala, Val, and Tyr adopts a stable 2.5-helical secondary structure in solution that is characterized by a pitch of approximately 5.1 Å and by the simultaneous presence of 12- and 14-membered hydrogen-bonded rings. Thus N,N′-linked oligoureas belong to the growing family of non-natural non-peptide oligomers with defined and predictable secondary structure.