Synthesis of the Tetracyclic Core of Daphnilactone B-Type and Yuzurimine-Type Alkaloids

The core of daphnilactone B-type and yuzurimine-type alkaloids was synthesized in only 16 steps from a known β-allyl-γ-butyrolactone. The key sequence of Vilsmeier–Haack cyclization and intramolecular azomethine ylide cycloaddition allowed the construction of, in a single step, three of the five rings common to all alkaloids found in both of these classes with perfect chemocontrol