uridine (11) with dimethyldioxirane proceeded from the α-face to give the 1‘,2‘-α-epoxide 12. Upon reacting with organoaluminum reagents, the 1‘,2‘-α-epoxide 12 underwent preferential syn-opening of the epoxide ring to yield the β-anomers of 1‘-methyl- (13β), 1‘-ethyl- (14β), 1‘-isobutyl- (15β), 1‘-ethynyl- (16β), 1‘-vinyl- (17β), and 1‘-phenyl- (18β) uridine derivatives, although the corresponding α-anomers