Stereocontrolled formal synthesis of (±)-platensimycin

The caged structure of platensimycin, known as Nicolaou's key intermediate for total synthesis of platensimycin, was synthesized stereoselectively by using the following key steps: (i) diastereoselective Diels-Alder reaction between gamma-benzoyloxy enone and tert-butyldimethylsiloxydiene, (ii) formation of a dihydropyran ring by intramolecular catalytic oxypalladation, and (iii) transannular radical cyclization of monothloacetal with tributyltin hydride and AIBN.