Dipolar Cycloaddition and Ring-Closing Metathesis in the Synthesis of the Tetracyclic ABCE Ring System of Manzamine A

The tetracyclic ABCE core ring system of the manzamine alkaloids was prepared with the correct relative stereochemistry by an intramolecular dipolar cycloaddition reaction of an azomethine ylide, followed by a ring-closing metathesis reaction.