title: Synthesis of spacer-equipped phosphorylated di-, tri- and tetrasaccharide fragments of the O-specific polysaccharide of Vibrio cholerae O139.
abstract: The synthesis of oligosaccharide fragments of the O-specific polysaccharide of Vibrio cholerae O139 containing a 4,6-cyclic phosphate galactose residue linked to GlcNAc is described. 8-Azido-3,6-dioxaoctyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->3)-2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-glucopyranoside, obtained by condensation of 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide and 8-azido-3,6-dioxaoctyl 2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-glucopyranoside, was converted to 8-azido-3,6-dioxaoctyl 3-O-benzyl-beta-D-galactopyranosyl-(1-->3)-2-acetamido-6-O-benzyl-2-deoxy-beta-D-glucopyranoside (6) by reductive opening of the acetal, followed by deacetylation and selective benzylation. Phosphorylation of 6 furnished two isomeric 4,6-cyclic 2,2,2-trichloroethyl phosphates. Glycosylation of the (S)-phosphate with 2,4-di-O-benzyl-3,6-dideoxy-alpha-L-xylo-hexopyranosyl bromide under halide-assisted conditions gave the desired tetrasaccharide, together with a trisaccharide. Global deprotection and reduction of the azide to an amine was effected by catalytic hydrogenation/hydrogenolysis to give the deprotected tetrasaccharide, which is functionalized for conjugation.
authors.affiliation: NIDDK, LMC, National Institutes of Health, Bethesda, MD 20892-0815, USA.
authors.forename: Bart
authors.initials: B
authors.lastname: Ruttens
authors.forename: Pavol
authors.initials: P
authors.lastname: Kovác
mesh_terms: D002240:Carbohydrate Sequence; D006001:Glycoconjugates / Q000737:chemistry; D006031:Glycosylation; D008969:Molecular Sequence Data; D019081:O Antigens / Q000737:chemistry*; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry*; D010766:Phosphorylation; D041242:Vibrio cholerae O139
chemical_list: D006001:Glycoconjugates; D019081:O Antigens; D009844:Oligosaccharides