Bicyclic Piperazine Mimetics of the Peptide β-Turn Assembled via the Castagnoli–Cushman Reaction

摘要

5-Oxopiperazine-2-carboxamides and respective carboxylic acids (obtained by the Castagnoli–Cushman reaction of protected iminodiacetic anhydride) were converted into cis - and trans -configured bicyclic piperazines containing two stereogenic centers. The latter are not only well-established mimetics of peptide β-turn but also attractive, high-F_(sp3) cores for drug design in general. The methodology was applied to the preparation of ring-expanded version of bicyclic piperazines not described in the literature.