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