Total Synthesis of Diterpenoid Steenkrotin A

A concise and diastereoselective total synthesis of the diterpenoid (±)-steenkrotin A is described for the first time. The strategy mainly features three key ring formations: 1) a rhodium-catalyzed O-H bond insertion followed by an intramolecular carbonyl-ene reaction to build up the tetrahydrofuran subunit; 2) sequential SmI2 -mediated Ueno-Stork and ketyl-olefin cyclizations to construct the [5,7] spirobicyclic skeleton; and 3) an intramolecular aldol condensation/vinylogous retro-aldol/aldol sequence to form the final six-membered ring with inversion of the relative configuration at the C7 position.