Difluoromethylene-C-Glycosides

1 Starting from Difluorovinyl Glycosides Saccharidic derivatives that have a difluoromethylene group in the pseudo-anomeric position are important synthetic intermediates for preparation of difluoro-C-glycosides, difluoro-C-phos-phonates, and difluoro-C-disaccharides. °  

The enolic double bond of a difluorovinyl group in the anomeric position is able to add a radical. It can thus afford a difluoro-C-glycoside, either directly or indirectly. When the alkylating radical is generated from a 6-halogenopyranoside, the reaction can lead to difluoro-C-disaccharide. These reactions are even more efficient if the radical has an electrophilic character (e.g., with an a-halogenoester instead of an alkyl radical). 

2 Starting from Difluorinated Nucleophilic Reagents Difluorinated 

3 Saccharidic Difluorophosphonates Difluoromethylene phospho-nates have been the focus of numerous works. Indeed, these compounds are able to mimic the phosphate bond in the synthesis of enzyme inhibitors. This interest is obvious for the furanose series in this case, they are non scissible analogues of 5-phosphate nucleosides (cf. Chapter 7). Difluoromethylene phosphonates can be prepared via a radical path starting from compounds that have the difluoromethylene moiety in the pseudo-anomeric position. Nevertheless, methods based on metal derivatives of difluorophosphonates are generally easier and broadly applicable. 

Indeed, metallation of diethyl difluoromethyl phosphonate affords an anion. This species can displace a primary triflate in position or add onto an aldehyde (in 

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