Tricyclic alkaloid core structures assembled by a cyclotrimerization-coupled intramolecular nucleophilic substitution reaction.

A facile approach to tricyclic alkaloid core structures was developed by sequencing a pyridine-forming [2 + 2 + 2] cyclotrimerization reaction with an intramolecular nucleophilic substitution. This methodology enabled the facile assembly of the spiroindolinone framework of citrinadins A and B, and cyclopiamine B.