The synthesis of 5-glycosyl isoxazoles with 3-alkyl-, 3-aryl, 3,4-dialkyl, 3-aryl-4-alkyl or 3-alkyl-4-bromo substituents is reported. Deoxyenuloses were obtained from reaction of 2,3-O-isopropylidene-D-glyceraldehyde and several phosphorus ylides, which contain a carbonyl group, by a Wittig reaction.C-glycosyl α,β-unsaturated ketones were obtained, with the polyhydroxylate chain lengthened by two or three carbon atoms. In the second phase the ketones were transformed into the correspondingC-glycosyl α,β-unsaturated ketoximes, leading to theC-glycosyl isoxazoles, which were converted into the title compounds via removal of the isopropylidene group of suitably protected carbohydrates. The solubility of the synthetizedC-glycosyl isoxazoles were modified by free hydroxyl groups in such a way that their behaviour against certain viruses and their potential antiviral activity could be studied.