A total synthesis of (plus-minus)-(alpha)-cyclopiazonic acid using a cationic cascade

The indolic terpene alkaloid (alpha)-cyclopiazonic acid 1 has been prepared in 11 steps from indole-4-methanol 6; the key step is a carbocationic cascade, terminated by a 4-nitrosulfonamide group and initiated by benzylic carbocation formation directly from the intermediate 9, which gives the tetracyclic product 10 in 74% yield.