Regio- and Stereoselective Synthesis of 1-/3-Sulfone Sugars Controlled by the Amount of SnCl ₄

A SnCl 4 -mediated regioselective sulfonylation of glycal donors with sulfinic acids enables stereodivergent synthesis of 1-sulfone sugars (0–10 mol % SnCl 4 ) or 3-sulfone sugars (1 equiv of SnCl 4 ), respectively. Mechanistic studies reveal that sulfinic acid can activate the C3 leaving group alone to form sulfone glycosides, while excess SnCl 4 promotes the 1,3-shift to afford 3-sulfone sugars. The protocol exhibits broad substrate scope, including late-stage modification of natural products, with excellent regio-/stereoselectivity.