Stereoselective Epimerizations of Glycosyl Thiols
Lisa M Doyle1, Shane O'Sullivan1, Claudia Di Salvo1
1School of Chemistry, National University of Ireland Galway , University Road, Galway, Ireland H91 TK33.
Abstract:
Glycosyl thiols are widely used in stereoselective S-glycoside synthesis. Their epimerization from 1,2-trans to 1,2-cis thiols (e.g., equatorial to axial epimerization in thioglucopyranose) was attained using TiCl4, while SnCl4 promoted their axial-to-equatorial epimerization. The method included application for stereoselective β-d-manno- and β-l-rhamnopyranosyl thiol formation. Complex formation explains the equatorial preference when using SnCl4, whereas TiCl4 can shift the equilibrium toward the 1,2-cis thiol via 1,3-oxathiolane formation.
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