title: Variations on the SnCl4 and CF3CO2Ag-promoted glycosidation of sugar acetates: a direct, versatile and apparently simple method with either alpha or beta stereocontrol.
abstract: Glycosidation of sugar peracetates (D-gluco, D-galacto) with SnCl(4) and CF(3)CO(2)Ag led to either 1,2-cis-, or 1,2-trans-glycosides, depending primarily on the alcohols used. In particular, 1,2-trans-glycosides, expected from acyl-protected glycosyl donors, were formed in high yields with alcohols sharing specific features such as bulkiness, presence of electron-withdrawing groups or polyethoxy motifs. In contrast, simple alcohols afforded approximately 1:1 mixtures of 2,3,4,6-tetra-O-acetyl, and 3,4,6-tri-O-acetyl 1,2-cis-glycosides due to anomerization and/or acid-catalyzed fragmentation of 1,2-orthoester intermediates. After reacetylation or deacetylation, acetylated or fully deprotected 1,2-cis-glycosides (alpha-D-gluco, alpha-D-galacto) were obtained in approximately 90% yields by a simple and direct method.
authors: Université de Lyon, Institut de Chimie et Biochimie Moléculaires et Supramoléculaires associé au CNRS, UMR 5246, Laboratoire de Chimie Organique 2, Bâtiment Curien, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne, France.
authors: Jia Lu
authors: JL
authors: Xue
authors: Samy
authors: S
authors: Cecioni
authors: Li
authors: L
authors: He
authors: Sébastien
authors: S
authors: Vidal
authors: Jean-Pierre
authors: JP
authors: Praly
mesh_terms: D000085:Acetates / Q000737:chemistry*; D002384:Catalysis; D006027:Glycosides / Q000737:chemistry*; D006031:Glycosylation; D013237:Stereoisomerism; D013379:Substrate Specificity; D017971:Tin Compounds / Q000737:chemistry*; D014269:Trifluoroacetic Acid / Q000737:chemistry*
chemical_list: D000085:Acetates; D006027:Glycosides; D017971:Tin Compounds; C041694:stannic chloride; D014269:Trifluoroacetic Acid