Glycosylations with a septanosyl fluoride donor lacking a C2 protecting group

Septanosyl fluorides, prepared from protected pyranoses, were used as donors in glycosylation reactions. The fluorides were synthesized by the addition of vinyl Grignard to the pyranoses followed by ozonolysis and then DAST-mediated fluorination. Activation in the presence of nucleophiles then provided the product glycosides. High α-stereoselectivity was observed for glycosylations using a donor that had a free C2 hydroxyl group; a model where the hydroxyl group participates to guide the stereochemical outcome is proposed.