Asymmetric Total Synthesis of Pedrolide.

The asymmetric total synthesis of pedrolide (>200 mg) with an unprecedented [5-5-5-6-6-3] hexacyclic core (pedrolane) was achieved. Its unique bicyclo[2.2.1]heptane ring system was efficiently constructed via an enantioselective ene reaction of cyclopentadiene followed by a Wittig reaction, isomerization, and a diastereoselective intramolecular Diels-Alder reaction cascade. The highly oxygenated carane [6-3] ring system was synthesized via a ring-closing metathesis reaction followed by an unusual free carbene cyclopropanation. Furthermore, the 12 contiguous stereocenters of pedrolide were installed diastereoselectively.