A formal synthesis of (−)-rotundone

(−)-Rotundone, an oxygenated sesquiterpene noted for intense woody and agarwood-like aromas, is a key odorant in perfumery and flavor chemistry. Its remarkable potency has attracted synthetic interest, yet most reported approaches rely on guaiene-type precursors, where difficult-to-separate off-notes and poor oxidation selectivity complicate efficient access. Here, we report an alternative route from commercially available (+)-(R)-limonene that improves step economy and yield through a modified ring-expansion step. This strategy enables direct construction of a cycloheptanone framework en route to the key Nazarov precursor to (−)-rotundone in seven steps with 13% overall yield.