3',3'-Difluoro-2'-hydroxymethyl-4',5'-unsaturated carbocyclic nucleosides 1-3 have been stereoselectively synthesized from ester 10, which can be conveniently prepared from 2,3-isopropylidene-d-glyceraldehyde 7 in five steps. The whole synthesis highlighted the stereoselective Reformatskii-Claisen rearrangement, ring-closing metathesis (RCM), and palladium-catalyzed allylic alkylation, in which the
4-difluoroisofagomine analogues were synthesized. These compounds were tested for inhibition of eight glycosidases. The 3R,5R isomer 1 is a new and potent inhibitor against β-glucosidase from almonds with Ki value of 1.2 μM. The influence of the gem-difluoromethylene group (CF2) on binding to glycosidases is discussed. It is concluded that only non-essential hydroxyl groups can be replaced by the gem-difluoro