Conversions of Nitroalkyl to Carbonyl Groups in Carbohydrates

Summary.  Since the development of the Sowden methodology in the middle of the twentieth century, several other efficient and complementary methods for the transformation of sugar nitromethyl groups to aldehyde functionalities in their free, hemiacetal, or otherwise derivatized forms have been developed. Hydrogen peroxide oxidation as well as ozonolysis of 1-deoxyalditol-1-nitronates in aqueous solution provide free aldoses, thus presenting alternatives to the well-known Nef reaction. When applied to 2,5- or 2,6-anhydro-1-deoxy-1-nitroalditols, also known also as glycosylnitromethanes, the Nef reaction fails, and the hydrogen peroxide oxidation overoxidizes the expected products to 2,5- or 2,6-anhydroaldonic acids. On the other hand, the ozonolysis of such compounds under pH-controlled conditions results in up to 85% of the interesting glycosylformaldehydes. The Nef reaction carried out in anhydrous low alcohols, however, has revealed a new conversion of glycosylnitromethanes to glycosylmethanal dialkyl acetals, even more interesting C-glycoside synthons. A similar acid-catalyzed methanolysis of 1-deoxyalditol-1-nitronates leads to methyl furanosides. Finally, a treatment of per-O-substituted glycosylnitromethanes with tributyltin hydride in boiling benzene causes their radical reduction under a nearly quantitative formation of glycosylmethanal oximes. Received November 12, 2001. Accepted November 20, 2001