Synthesis of cyclically constrained sugar derived α/β- and α/γ-peptidesElectronic supplementary information (ESI) available: NMR spectra of all new compounds. See DOI: 10.1039/c2ob26992a

A general approach to enantiopure conformationally constrained sugar derived α/β- and α/γ-peptides has been established. Five-membered ring α/β-peptides were synthesized via formyl C -glycofuranosides, easy available from hexose-derived azido-2- equatorial -OH-glycopyranosides by DAST-promoted ring contraction. By means of a regioselective oxidation with TEMPO at C-6 of hexose-derived 3-azido glycopyranosides as the key step, two- and three-residue α/γ-peptides having a six-membered ring were obtained in good yields and under very simple experimental conditions. An economical, diversity-oriented strategy to access novel enantiopure, both five- and six-membered ring α/β- and α/γ-hybrid peptides containing sugar amino acid residues has been developed.