S-Methylation of α-ketothioethers of sugars gave in good yields the corresponding sulfonium derivatives whose alkaline treatement led to the expected, stable, carbohydrate sulfylides3and .8. When asymmetric, the sulfur atom is configurationally stable as shown by dynamic NMR. These sugar sulfylides are prone toStevensrearrangement, react withMichaelacceptors to give cyclopropane derivatives and most unexpectedly lead to “exotic” oxathiolenedioxide C-glycosides when reacted with sulfenes.