A stereoselective total synthesis of (+)-marrubiin has been accomplished starting from a chiral building block via the CyNH2-promoted Pauson–Khand reaction (PKR) followed by oxidative cleavage of the resultant cyclopentenone ring. Two successive oxidations and internal transacetalization culminated in the total synthesis of the antispasmodic labdane diterpenoid (−)-marrulibacetal.