A new route to BCD tricyclic fragment of C19-diterpenoid alkaloids via intramolecular Pauson-Khand reaction followed by anionic 1,2-migration rearrangement

A robust synthetic approach for the rapid assembly of the bridged tricyclic BCD ring system of C19-diterpenoid alkaloids bearing a characteristic hydroxy group on ring C has been developed. The synthesis features an efficient intramolecular Pauson-Khand reaction and an exclusive anionic 1,2-migration rearrangement to generate the unique bicyclo[3.2.1]octane moiety of the CD-ring on the seven-membered B-ring.