Total Synthesisof (±)-Caryopincaolide A

The first total synthesis of (±)-caryopincaolide A, a rearranged abeo-abietane diterpenoid containing a 5/6/6 fused skeleton and three contiguous all-carbon quaternary centers, is described. The route installs the aromatic ring at an early stage and assembles the congested framework in a C/B → A sequence. An Fe(acac)3/PhSiH3-mediated reductive alkene–enone coupling is the key skeleton-forming step, providing the rearranged tricyclic core in 93% yield. Carbonyl transposition, β-keto ester alkylation, ketone hydrogenolysis, and an ortho-quinone-mediated aromatization/lactonization sequence complete the synthesis in 16 steps and 3.0% overall yield.