Many other groups have undertaken similar efforts, but successful synthetic approaches to 1 have only recently been reported. The first total synthesis of nimbolide was accomplished in 2024 by the Qin group, and since then, two formal syntheses have been reported by Li and Ma (Figure ). These strategies all rely on accessing transdecalin derivative 5 which possesses a free alcohol at C7 that can act as a nucleophile in an O-H insertion reaction. To access this material, the Qin group utilized a degradative approach from dehydroabietic acid. Li and coworkers performed enzymatic oxidation of 9,11dehydrosclareolide to afford an appropriately oxidized precursor to 5, and Ma and coworkers constructed the Bring through a reductive Heck reaction en route to 5. Still, despite extensive investigation, the key O-H etherification between 5 and 6 proceeded with poor diastereoselectivity at C15, resulting in a modest isolated yield (5→7). Furthermore, the exocyclic olefin in 7 caused poor selectivity during cyclization, where a mixture of 5-exo (1) and 6-endo (8) products were obtained under radical cyclization conditions. Given the successes of previous groups, but keeping the challenges faced in each synthesis in mind, we arrived at our final retrosynthetic analysis (Figure ). From nimbolide (1), we planned to form the lactone last and excise the eastern cyclopentene through sequential radical cyclization and etherification reactions. This would deliver vinyl epoxide 10 as the key precursor to 1. This intermediate had two subtle characteristics that we hoped would overcome the selectivity problems described in previous syntheses. First, the olefin that would undergo radical addition was endocyclic, so there would be no possibility for a 6-endo cyclization as observed by Qin. Second, we intended to use alcohol 9 as a nucleophile in an etherification reaction and vinyl epoxide 10 would serve as an electrophile. We expected that the bicyclic system might properly control an intermolecular SN1 etherification by directing the nucleophile to approach from the bottom face, thus overcoming the poor diastereoselectivity observed by others.