An improved procedure for the analysis of linkage positions in 2-acetamido-2-deoxy-d-glucopyranosyl residues by the reductive-cleavage method
โ Scribed by Anello J. D'Ambra; Gary R. Gray
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 829 KB
- Volume
- 251
- Category
- Article
- ISSN
- 0008-6215
No coin nor oath required. For personal study only.
โฆ Synopsis
The conditions of the reductive-cleavage method were modified to allow simultaneous analysis of 2-acetamido-2-deoxy-o-glucopyranosyl residues and monosaccharides of other classes. Methyl 2-deoxy-3,4,6-tri-0-methyl-2-(N-methylacetamidoride was found to undergo transglycosidation under reductive-cleavage conditions when the reaction was quenched with an alcohol. Transglycosidation proceeded via an oxaxolinium-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 (Me,SiOSO,CFs), 4 h were required for complete conversion of the substrate into this intermediate, which was then trapped with methanol-d,. When the reaction was conducted in the presence of a mixture of trimethylsilyl methanesulfonate (MesSiOSOaMe) and boron trifluoride etherate (BF, OEt,) or with BF, . OEt a alone, 24 h and 48 h, respectively, were required for complete conversion. The a 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 'H 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.
๐ SIMILAR VOLUMES
The fate of 4-linked D-glucopyranosyluronic residues under reductive-cleavage conditions was investigated by using the Klebsiella aerogenes type 54 strain A3 capsular polysaccharide. Treatment of the fully methylated polysaccharide with triethylsilane and trimethylsilyl trifluoromethanesulfonate in