289653-59-4Relevant academic research and scientific papers
Synthesis of Thio-Linked Disaccharides by 1→2 Intramolecular Thioglycosyl Migration: Oxacarbenium versus Episulfonium Ion Intermediates
Johnston, Blair D.,Pinto, B. Mario
, p. 4607 - 4617 (2007/10/03)
The conversion of 1,1′-thio-linked glucopyranosyl α-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 α- and β-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.
