A Comprehensive Synthetic Exploration of Euolutchuols A, B, C, and D, Hinokiol, and Related Abietane Diterpenoids

We report a unified enantioselective total synthesis of euolutchuols A–D and related aromatic abietanes, and hinokiol. The absolute structures of euolutchuols were established by synthesizing possible isomers and correlating their spectral and optical data with reported values. Enantioenriched abietatetraene ( 5 ), prepared through a non‐enzymatic cationic cyclization, served as a common intermediate for all targets. The C‐15 stereocenter of the isopropyl side chain was installed using three distinct asymmetric approaches: enantioselective hydroboration with chiral boranes, Cu‐catalyzed hydroboration, and Sharpless dihydroxylation followed by reductive hydrogenolysis. The C‐12 hydroxyl group was installed via two complementary routes: Friedel–Crafts acylation, subsequent Baeyer–Villiger oxidation, or by a direct regioselective oxygenation. The C2–C3 syn ‐diol motif was constructed either by direct asymmetric dihydroxylation or by an α‐oxidation/diketone reduction sequence. A CBS reduction was employed to access C‐15 center of euolutchuol C. Two unusual reactions are disclosed: (i) a selective DMP‐mediated over‐oxidation of a styrenyl double bond to ketone to get abietatriene‐3,15‐dione; and (ii) a Pd/C catalyzed over‐reduction in the hydrogenolysis of a 1,2‐diol, which is effectively utilized for the synthesis of hinokiol.