Abstract : O-Glycoconjugates and carbohydrate-based molecules are natural compoundsimplied in many biological processes. However, their properties are burdened by the low invivo stability of the osidic bond. It is thus interesting to develop non hydrolyzable mimetics.We were interested in the replacement of the intracyclic oxygen by a gem-difluoromethylenegroup.The synthesis of difluorinated carbocyclic analogues of 5-deoxypentofuranoses and1-amino-5-deoxypentofuranoses is described. The sequence involves an addition ofPhSeCF2TMS to carbohydrate-derived aldehydes or their corresponding tertbutanesulfinyliminesfollowed by a radical cyclization. The stereochemical outcome of these two key steps was studied, and then this strategy was applied to CF2-carbasugars, inparticular of the CF2-carbocyclic analogue of D-arabinose.