The First Dye-sensitized Photooxygenation of 2-(C-glycosyl)furans. One-Pot Stereoselective Approach to New Carbohydrate Derivatives

The singlet oxygen oxygenation of 2-(α-C-glucopyranosyl)furans 1 leads readily and diastereoselectivity to the corresponding endoperoxides 2 whose fate can be controlled. Compounds 2 thermally rearrange into cis-dicarbonyl-α-O-glucosides 3 while by reduction they afford the cis-C-analogs 5. The latter readily convert to trans-8, which by silica gel chromatography tautomerize into β-anomers 9.