arsenic ylides with pyranose and furanose carbohydrates mainly leads to E-olefinic derivatives. Cyclisation of the olefinic derivatives obtained from 2,3,4,6-tetra-O-benzyl-D-glucose and D-galactose, promoted by ZnBr2, gives C-glycosyl compounds with high stereoselectivity. One the other hand, reaction of the corresponding arsonium salt, in presence of zinc, with a furanosederivative gives directly and