title: Synthesis of disaccharides related to the O-specific polysaccharide of Salmonella typhimurium.
abstract: Methyl 2-O-benzyl-4,6,-O-benzylidene-alpha-D-mannopyranoside (13) has been glycosylated with 3,6-dideoxy-2,4-di-O-p-nitrobenzoyl-alpha-D-xylo-hexopyranosyl bromide (4) and its enantiomer (5) using mercury cyanide as catalyst and toluene and nitromethane as solvent. The anomeric ratio has been determined by 1H NMR spectroscopy and is reversed going from the D to the L compound. Glycosylation of 13 with 2-O-benzyl-3,6-dideoxy-4-O-p-nitrobenzoyl-alph-D-xylo-hexopyranosyl bromide (9) under similar reaction conditions gives exclusively the alpha-linked disaccharide while glycosylation using 2,4-di-O-benzyl-3,6-dideoxy-alpha-D-xylo-hexopyranosyl chloride (12) gives a 1:3 mixture of beta- and alpha-linked disacchrides. Glycosylation of 13 with 12, catalyzed by tetrabutylammonium bromide at elevated temperature, yields exclusively the alpha-linked disaccharide. The conformation of two of the deprotected disaccharides has been determined using hard sphere calculations and high field NMR data.
mesh_terms: D002236:Carbohydrate Conformation; D004187:Disaccharides / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D011135:Polysaccharides, Bacterial; D012486:Salmonella typhimurium / Q000276:immunology*; D013329:Structure-Activity Relationship
chemical_list: D004187:Disaccharides; D007202:Indicators and Reagents; D011135:Polysaccharides, Bacterial