Total syntheses of (±)-fawcettimine, (±)-fawcettidine, (±)-lycoflexine, and (±)-lycoposerramine-Q.

The total syntheses of four fawcettimine-related Lycopodium alkaloids, (±)-fawcettimine, (±)-fawcettidine, (±)-lycoposerramine-Q, and (±)-lycoflexine, were completed in a highly stereoselective manner. The Pauson-Khand reaction of 4-methylidene-6-siloxyoct-1-en-7-yne followed by regio- and stereoselective hydrogenation led to the short-step preparation of the bicyclo[4.3.0]nonenone intermediate bearing a methyl group with the required stereochemistry. The subsequent chemical manipulation of the bicyclic compound afforded the 6-5-9-membered tricyclic dioxo compound, which was then transformed into the four targeted alkaloids in an alternative and more efficient fashion.