Dye-sensitized photooxygenation of sugar furans: novel bis-epoxide and spirocyclic C-nucleosides

Dye-sensitized photooxygenation of 2-methyl 5-(2,3,5-tri-O-acetyl-β-d-ribofuranosyl)furoate leads to (1S,4R)-endo-peroxide, highlighting a high facial diastereoselectivity. This endo-peroxide rearranges into syn-(1R,2R:3S,4R)-diepoxide C-nucleoside, while by Et2S-reduction followed by NEt3 catalysis affords a spirocyclic C-nucleoside.