Glycosyl sulfonate

Glycosyl sulfones, normally of low reactivity, have been reported as glycosyl donors, activated by magnesium bromide etherate.188... 

Glycosyl residues, nomenclature, 125 Glycosyl sulfones, as glycosyl donors, 199— 200... 

Scheme 4.55 Glycosylation with a 2,3-unsaturated glycosyl sulfone.

General Procedure for the Preparation of Diazirines from Glycosyl Sulfonates... 

Similarly, starting from 2,3 5,6-di-0-isopropylidene-D-mannofuranose 72, a one-pot procedure that implies the synthesis of glycosyl sulfones by Horner-Wadsworth-Emmons olefination with phosphonate 73, followed by subsequent Michael addition and Ramberg-Backlund reaction92 gives compound 74 in 78% yield93 (Scheme 24). 

In conclusion, the Ramberg- Backlund reaction of glycosyl sulfones is a useful and general route to a variety exo glycals. Simple conversions of the exo-glycals make available a variety of C-glycosides. 

An alternative to the above methods is the activation of hemiacetals via glycosyl sulfonates 185 (Scheme 4.36). 

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