The synthesis of the unsaturated 4,6-dideoxy-3-fluoro-2-keto-β- d-glucopyranosyl nucleosides of 5-fluorouracil ( 6a), N 6-benzoyl adenine ( 6b), uracil ( 6c), thymine ( 6d) and N 4-benzoyl cytosine ( 6e), is described. Monoiodination of compounds 1a, b, followed by acetylation, catalytic hydrogenation and finally regioselective 2′- O-deacylation afforded the partially acetylated dideoxynucleoside analogues of 5-fluorouracil ( 5a) and N 6-benzoyl adenine ( 5b), respectively. Direct oxidation of the free hydroxyl group at the 2′-position of 5a, b, with simultaneous elimination reaction of the β-acetoxyl group, afforded the desired unsaturated 4,6-dideoxy-3-fluoro-2-keto-β- d-glucopyranosyl derivatives 6a, b. Compounds 1c– e were used as starting materials for the synthesis of the dideoxy unsaturated carbonyl nucleosides of uracil ( 6c), thymine ( 6d) and N 4-benzoyl cytosine ( 6e). Similarly a protection-selective deprotection sequence followed by oxidation of the free hydroxyl group at the 2′-position of the dideoxy benzoylated analogues 9c– e with simultaneous elimination reaction of the β-benzoyl group, gave the desired nucleosides 6c– e. None of the compounds was inhibitory to a broad spectrum of DNA and RNA viruses at subtoxic concentrations. The 5-fluorouracil derivative 6a was more cytostatic (50% inhibitory concentration ranging between 0.2 and 12 μM) than the other compounds.