Trisequential photooxygenation reaction: application to the synthesis of carbasugars.

4,5-Dimethylenecyclohex-1-ene was subjected to a photooxygenation reaction to introduce oxygen functionalities. The endoperoxide obtained underwent an ene-reaction to form hydroperoxides with 1,3-diene structures. Further addition of singlet oxygen to the diene units resulted in the formation of tricyclic hydroperoxides having three oxygens in the molecule. Cleavage of the oxygen-oxygen bonds followed by epoxidation of the remaining C-C double bond and concomitant ring-opening reaction furnished the isomeric carbasugars.