2‐Deoxyglycosyl fluorides in oligosaccharide synthesis

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Abstract
3,4‐Di‐O‐acetyl‐2,6‐dibromo‐2,6‐dideoxy‐α‐D‐mannopyranosyl fluoride (1) was treated with Lewis acid catalysts to give α‐glycosides exclusively. Reactions with α‐ and β‐glucosyl analogs yield α/β mixtures under the same conditions. With no assistance of anchimeric substituents at C‐2 the stereoselectivity is directed by a glycosyl fluoride/catalyst/solvent complex. As shown in the 2‐deoxy‐arabino‐hexopyranosyl series this leads to improved α/β ratios and yields.