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An improved procedure for the analysis of linkage positions in 2-acetamido-2-deoxy-d-glucopyranosyl residues by the reductive-cleavage method

โœ 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

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โœฆ 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.


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