2,3-Anhydrosugars in glycoside bond synthesis: application to furanosyl azides and C-glycosides

The preparation of 2-deoxy-2-thiotolylfuranosyl azides and C-glycosides from a 2,3-anhydrosugar thioglycoside with the d-lyxo stereochemistry is described. The reaction is performed by treatment of the thioglycoside with a trimethylsilylated nucleophile in the presence of BF3·OEt2. This approach provides a convenient route to the preparation of the corresponding 2-deoxy-furanosyl azides and C-glycosides. In contrast, the use of an isomeric substrate, with the 2,3-anhydro-d-ribo stereochemistry, gave these products in low to modest yield.