β-TurnInductionby a DiastereopureAzepane-DerivedQuaternaryAminoAcid

β-Turns are one of the most common secondary structures found in proteins. In the interest of developing novel β turn inducers, a diastereopure azepane-derived quaternary amino acid has been incorporated into a library of simplified tetrapeptide models in order to assess the effect of the azepane position and peptide sequence on the stabilization of β-turns. The conforma tional analysis of these peptides by molecular modeling, NMR spectroscopy, and X-ray crystallography showed that this azepane amino acid is an effective β-turn inducer when incorporated at the i + 1 position. Moreover, the analysis of the supramolecular self assembly of one of the β-turn-containing peptide models in the solid state reveals that it forms a supramolecular helical arrangement while maintaining the β-turn structure. The results here presented provide the basis for the use of this azepane quaternary amino acid as a strong β-turn inducer in the search for novel peptide-based bioactive molecules, catalysts, and biomaterials.This research was supported by the CSIC grant PIE 202180E073. D.N.-V. is supported by a fellowship from the Fundación General CSIC’s ComFuturo program, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 101034263. Com pound 2 experiments were performed at BL13-XALOC beamline at ALBA Synchrotron with the collaboration of ALBA stafPeer reviewe