A Novel and Highly Stereoselective Intramolecular Formal [3+3] Cycloaddition Reaction of Vinylogous Amides Tethered with α,β-Unsaturated Aldehydes: A Formal Total Synthesis of (+)-Gephyrotoxin.

Complex piperidinyl heterocycles (for example, 2) were accessed by using a novel intramolecular formal [3+3] cycloaddition reaction of vinylogous amides tethered with enals (for example, 1). This method has been applied to a formal total synthesis of (+)-gephyrotoxin (3).