Novel conformationally restricted glycoamino acids from glyco-α-aminonitriles as potent turn mimics in peptide synthesis

Abstract

Our previously described glycoaminocyanation procedure using Ti(O iPr) 4 and TMSiCN has been applied to introduce amino acid and peptide moieties on a monosaccharide. Selective reduction using NaNH 4–CoCl 2 and Pd(C), respectively, is described. Restricted conformation of the new glycoamino acids favours intramolecular cyclisation to give the corresponding oxopiperazine 5a– b and 12a– b . The target acyclic compound I was obtained when the peptide derivative was displaced from the complex using KCN. Hydrolysis of the glycospirohydantoin 18 to give the glycoamino acid II is also described.