A concise approach to synthesize the tetracyclic framework of the marine diterpenoid plumisclerin A is described. Starting from commercially available iridoid genipin, a highly selective intermolecular Diels-Alder reaction was utilized to construct the A/B/C tricycle. Later, a four-step sequence involving stereoselective epoxidation and Dauben oxidative rearrangement was developed to introduce the requisite enone moiety. The unique tricyclo[4,3,1,01,5]decane motif was successfully forged via a late-stage SmI2-mediated reductive coupling.