期刊
JOURNAL OF ORGANIC CHEMISTRY
卷 65, 期 15, 页码 4607-4617出版社
AMER CHEMICAL SOC
DOI: 10.1021/jo000226k
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The conversion of 1,1'-thio-linked glucopyranosyl alpha-D-mannopyranosides to 1,2-thio-linked methyl sophorosides or methyl kojibiosides is described. The method involves the 1-->2-migration of the thioglucopyranosyl portion of the nonreducing disaccharide with inversion of configuration at C-2 of the mannopyranose ring and concomitant formation of the methyl glucopyranoside. The thioglucosyl migration does not occur when electron-withdrawing benzoate protecting groups are present. The rearrangement occurs with retention of configuration in the migrating thioglucoside but the methyl glycoside is formed as a mixture of alpha- and beta-isomers. This is attributed to a mechanism involving an oxacarbenium-ion intermediate rather than an episulfonium-ion intermediate. The relevance of this work to recent theoretical predictions concerning the relative stability of such intermediates is discussed.
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