Highly Stereoselective Nucleophilic Addition of Difluoromethyl-2-pyridyl Sulfone to Sugar Lactones and Efficient Synthesis of Fluorinated 2-Ketoses

Nucleophilic addition of difluoromethyl-2-pyridyl sulfone to sugar lactones proceeded with good yield and excellent stereoselectivity. The hitherto unknown direct addition intermediates are stable and capable of useful conversions: Formal elimination of the anomeric hydroxy and sulfonyl groups yielded a 1-deoxy-1-difluoromethylene mannopyranose derivative. Directly from sugar lactones, by nucleophilic addition and subsequent one-pot reduction with allylmagnesium chloride, unprecedented fluorinated 2-ketose analogues were prepared efficiently.