Asymmetric total synthesis of alkaloids 223A and 6-epi-223A.

Concise and asymmetric total synthesis of the title compounds are described. The key ring system was constructed using an intramolecular Schmidt reaction on a norbornenone derivative, which was subsequently subjected to ring-opening metathesis followed by reduction. An unusual isomerization of the C-6 ethyl group afforded the desired stereochemistry of the natural product. The synthesis is readily adaptable to analogue production.