title: Synthesis of four structural elements of xylose-containing carbohydrate chains from N-glycoproteins.
abstract: The synthesis of the oligosaccharides beta-D-Xylp-(1----2)-beta-D-Manp-OMe (12), beta-D-Xylp-(1----2)-[alpha-D-Manp-(1----6)]-beta-D-Manp+ ++-OMe (17), beta-D-Xylp-(1----2)-[alpha-D-Manp-(1----3)]-beta-D-Manp+ ++-OMe (21), and beta-D-Xylp-(1----2)-[alpha-D-Manp-(1----3)] [alpha-D-Manp-(1----6)]-beta-D-Manp-OMe (25) is described. Methyl 3-O-benzyl-4,6-O-isopropylidene-beta-D-mannopyranoside (6) was prepared from the corresponding glucoepimer (4) by oxidation, followed by stereoselective reduction. Condensation of 6 with 2,3,4-tri-O-acetyl-alpha-D-xylopyranosyl bromide in the presence of mercuric cyanide gave a 1:9 mixture of methyl 3-O-benzyl-4,6-O-isopropylidene-2-O-(2,3,4- tri-O-acetyl-alpha- (7a) and -beta-D-xylopyranosyl)-beta-D-mannopyranoside (7), and then 7 was converted into the acetylated disaccharide-glycoside 11. Regioselective mannosylation, with 2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl bromide, at position 6 of deisopropylidenated 7 (8), using mercuric bromide as a promoter, afforded the trisaccharide-glycoside derivative 13, which was transformed into the acetylated trisaccharide-glycoside 16. The disaccharide derivative 10, obtained from 8, and the trisaccharide derivative 15, obtained from 13, were glycosylated at position 3 with O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)trichloroacetimidate (19), using trimethylsilyl triflate as a promoter, giving rise to acetylated tri- (20) and tetra-saccharide (24) derivatives, respectively. O-Deacetylation of 11, 16, 20, and 24 gave 12, 17, 21, and 25, respectively.
authors.affiliation: Department of Bio-Organic Chemistry, Utrecht University, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Kerékgyártó
authors.forename: J P
authors.initials: JP
authors.lastname: Kamerling
authors.forename: J B
authors.initials: JB
authors.lastname: Bouwstra
authors.forename: J F
authors.initials: JF
authors.lastname: Vliegenthart
authors.forename: A
authors.initials: A
authors.lastname: Lipták
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006023:Glycoproteins; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009844:Oligosaccharides / Q000138:chemical synthesis*; D014994:Xylose
chemical_list: D006023:Glycoproteins; D007202:Indicators and Reagents; D009844:Oligosaccharides; D014994:Xylose