C-glycosides. 3. 1,3-dipolar cycloaddition on nitrile and nitrilimine oxides

1.3-dipolar cycloaddition of alkenes (or alkynes) on sugars-nitriloxides and nitrilimines led respectively to 3-glycosyl-isoxazolines (or isoxazoles) and 3-glycosyl-pyrazolines (or pyrazoles). 5-glycosyl-isoxazolines were similarly prepared from arylnitriloxides and α- or ω-unsaturated sugars. These new C-glycosides are potential antiviral and anti-tumor agents.