title: Synthesis of methyl O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-D-galactopyranosides specifically deoxygenated at position 3, 4, or 6 of the galactose residue.
abstract: The title disaccharides were synthesized by condensation of 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl bromide with suitably protected, deoxygenated derivatives of methyl alpha-D-galactopyranoside. Deoxygenation was achieved via activation of a protected methyl alpha-D-gluco- or galacto-pyranoside with N,N'-thiocarbonyldiimidazole followed by treatment with tributyltin hydride and azobisisobutyronitrile. At position 3, the deoxygenation was more successful when performed with the tri-O-benzoylated precursor, rather than the tri-O-benzylated one. The corresponding nucleophile was obtained by benzylidenation of the methyl 3-deoxy-alpha-D-xylo-hexopyranoside. The preparation of the glycosyl acceptor deoxygenated at position 4 could be pursued starting from derivatives having either the D-galacto or the D-gluco configuration. The pathway involving the former was found superior.
authors.affiliation: NIDDK, National Institutes of Health, Bethesda, MD 20892.
authors.forename: L A
authors.initials: LA
authors.lastname: Mulard
authors.forename: P
authors.initials: P
authors.lastname: Kovác
authors.forename: C P
authors.initials: CP
authors.lastname: Glaudemans
mesh_terms: D000907:Antibodies, Bacterial / Q000276:immunology; D000937:Antigen-Antibody Reactions; D000942:Antigens, Bacterial / Q000276:immunology; D002240:Carbohydrate Sequence; D004187:Disaccharides / Q000138:chemical synthesis*; D000939:Epitopes / Q000737:chemistry*; D005643:Fucose / Q000031:analogs & derivatives*; D008070:Lipopolysaccharides / Q000276:immunology; D008969:Molecular Sequence Data; D012762:Shigella dysenteriae / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D004187:Disaccharides; D000939:Epitopes; D008070:Lipopolysaccharides; C086572:methyl O-rhamnopyranosyl-(1-2)-3-deoxygalactopyranoside; C086573:methyl O-rhamnopyranosyl-(1-2)-4-deoxygalactopyranoside; C086574:methyl O-rhamnopyranosyl-(1-2)-6-deoxygalactopyranoside; D005643:Fucose