Novel, Amino Acid-Derived Heterobicycles: Scaffolds for β-Turn Mimics and Targets for Combinatorial Synthesis

Abstract

Interest in combinatorial synthetic design and in α-turn mimics led to the development of a short synthesis of three ring systems (1—3) from cyclization of hydroxyacyl-dipeptide aldehyde derivatives, 6—8, with trifluoroacetic acid in acetone. The bicyclic products 1 and 2 were formed as single diastereomers with the benzyl substituent in the exo orientation, as determined by X-ray crystallography; the benzo analogs 3 were formed as mixtures of epimers, with the endo isomers predominating.