title: An improved procedure for the analysis of linkage positions in 2-acetamido-2-deoxy-D-glucopyranosyl residues by the reductive-cleavage method.
abstract: The conditions of the reductive-cleavage method were modified to allow simultaneous analysis of 2-acetamido-2-deoxy-D-glucopyranosyl residues and monosaccharides of other classes. Methyl 2-deoxy-3,4,6-tri-O-methyl-2-(N-methylacetamido)-beta-D-glucopyran oside was found to undergo transglycosidation under reductive-cleavage conditions when the reaction was quenched with an alcohol. Transglycosidation proceeded via an oxazolinium-ion intermediate, which then acted as a glycosyl donor to form an anomerically pure product. Time-course studies showed that in the presence of trimethylsilyl trifluoromethanesulfonate (Me3SiOSO2CF3), 4 h were required for complete conversion of the substrate into this intermediate, which was then trapped with methanol-d4. When the reaction was conducted in the presence of a mixture of trimethylsilyl methanesulfonate (Me3SiOSO2Me) and boron trifluoride etherate (BF3.OEt2) or with BF3.OEt2 alone, 24 h and 48 h, respectively, were required for complete conversion. The alpha anomer was unreactive after 24 h under all conditions, confirming earlier results. Reaction with racemic 2-butanol yielded a pair of diastereomers, in a 1:1 ratio, which were distinguishable by their GLC retention times and their 1H NMR spectra. Reaction with (S)-2-butanol gave only one of the diastereomeric products. These experiments demonstrated the feasibility of using the reductive-cleavage method to determine the absolute configuration of 2-acetamido sugars.
authors.affiliation: Department of Chemistry, University of Minnesota, Minneapolis 55455.
authors.forename: A J
authors.initials: AJ
authors.lastname: D'Ambra
authors.forename: G R
authors.initials: GR
authors.lastname: Gray
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry*; D002384:Catalysis; D002849:Chromatography, Gas; D009005:Monosaccharides / Q000032:analysis; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000737:chemistry*; D017421:Sequence Analysis / Q000379:methods*
chemical_list: D009005:Monosaccharides; D011134:Polysaccharides; D000117:Acetylglucosamine