title: Stereoselective synthesis of alpha- and beta-glycosylamide derivatives from glycopyranosyl azides via isoxazoline intermediates.
abstract: Treatment of 2-acetoxy glycopyranosyl azides with Ph3P gave isoxazolines by ring closure of the phosphorimine. Coupling of in situ generated isoxazolines with acylating reagents gave mixtures of alpha- or beta-glycopyranosyl amides. The alpha/beta ratio depended upon the acylating reagent and metal salts employed. For example, coupling of isoxazoline 3 with Z-Asp-(SPy)-OBn in the presence of CuCl2 gave exclusively alpha-N-glucopyranosylasparagine derivative 8. This general procedure has been applied to mono-, di-, and trisaccharide systems.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.
authors.forename: Fehmi
authors.initials: F
authors.lastname: Damkaci
authors.forename: Philip
authors.initials: P
authors.lastname: DeShong
mesh_terms: D000595:Amino Acid Sequence; D001386:Azides / Q000737:chemistry*; D006020:Glycopeptides / Q000138:chemical synthesis*; D007555:Isoxazoles / Q000737:chemistry*; D008969:Molecular Sequence Data; D011714:Pyrans / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001386:Azides; D006020:Glycopeptides; D007555:Isoxazoles; D011714:Pyrans