Construction of the [7–5–5] Tricyclic Core of Daphniphyllum Alkaloids via a Cationic Cascade Reaction

The [7–5–5] tricyclic core of daphniphyllum alkaloids, containing contiguous stereogenic centers at C14 and C15 and a tetrasubstituted alkene moiety between C9 and C10, was constructed via a cascade reaction that involved an electrocyclic reaction of a pentadienyl cation and intramolecular interception of the resultant cyclopentenyl cation.