title: Synthesis of methyl O-(3-deoxy-3-fluoro-beta-D-galactopyranosyl)-(1----6)-O-beta-D- galactopyranosyl-(1----6)-3-deoxy-3-fluoro-beta-D-galactopyranoside and related N.M.R. studies.
abstract: Sequential tritylation, benzoylation, and detritylation of methyl 3-deoxy-3-fluoro-beta-D-galactopyranoside gave crystalline methyl 2,4-di-O-benzoyl-3-deoxy-3-fluoro-beta-D-galactopyranoside (9), which was used as the initial nucleophile in the synthesis of the target oligosaccharide (16). Treatment of 9 with 2,3,4-tri-O-benzoyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide gave the corresponding disaccharide derivative 13, having a selectively removable blocking group at O-6'. Debromoacetylation of 13 afforded the disaccharide nucleophile 14 which, when treated with 2,4,6-tri-O-benzoyl-3-deoxy-3-fluoro-alpha-D-galactopyranosyl bromide, gave the fully protected trisaccharide 15. Debenzoylation of 15 gave the title glycoside 16. Condensation reactions were performed with silver trifluoromethane-sulfonate as a promoter in the presence of sym-collidine under base-deficient conditions, and gave excellent yields of the desired beta(trans)-products. Analyses of the 1H- and 13C-n.m.r. spectra, as well as determination of the JCF and JHF coupling constants, were made by using various one- and two-dimensional n.m.r. techniques.
mesh_terms: D002236:Carbohydrate Conformation; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009904:Optical Rotation; D014312:Trisaccharides / Q000138:chemical synthesis*
chemical_list: D007202:Indicators and Reagents; D014312:Trisaccharides; C046976:methyl O-(3-deoxy-3-fluoro-galactopyranosyl)(1-6)-O-galactopyranosyl(1-6)-3-deoxy-3-fluorogalactopyranoside