Total Synthesis of (−)-Oridonin: An Interrupted-Nazarov Approach

An enantioselective total synthesis of (−)-oridonin is accomplished based on a key interrupted-Nazarov reaction. The stereochemistry of the Nazarov/Hosomi-Sakurai cascade was first explored to forge a tetracyclic skeleton with challenging quaternary carbons. A delicate sequence of two ring-rearrangements and late-stage redox manipulations were carried out to achieve the de novo synthesis of this highly oxidized kaurenoid.