Diastereoselective formal synthesis of a monoterpene alkaloid, (-)-incarvilline, the key intermediate for the synthesis of (-)-incarvillateine, was achieved by using an intramolecular Pauson-Khand reaction of (S)-N-[(E)-2-butenyl]-N-(3-butynyl-2-methoxymethoxy)-p-toluenesulfonamide as a key step.