Phe-Ala-Based Diazaspirocyclic Lactam as Nucleator of Type II′ β-Turn

The synthesis of a novel Phe-Ala dipeptide mimic, built up on a diazaspirocyclic lactam core, is presented. This new scaffold was evaluated for conformational mimicry of reverse turn by combining molecular modeling, IR, NMR, and X-ray diffraction experiments. All these tools agree on the presence of a strong intramolecular hydrogen bond, thus demonstrating the ability of this spiro compound to act as a type II′ β-turn inducer.