Synthesis of (+)-Hinokiol, (+)-Hinokione, (+)-Salviol, and (+)-2-Oxoferruginol

Reduction of abieta-5,8,11,13-tetraen-3-one with lithium aluminium hydride afforded the corresponding alcohol, which was submitted to catalytic hydrogenation to yield abieta-8,11,13-trien-3β-ol (7) together with its 5βH-isomer. Acetylation of 7, followed by the Friedel-Crafts acylation, afforded 3β-acetoxy-12-acetylabieta-8,11,13-triene. This compound was converted into 3β,12-diacetoxyabieta-8,11,13-triene (11) by the Baeyer-Villiger oxidation. Treatment of 11 with lithium aluminium hydride yielded hinokiol, which was oxidized to hinokione. Subsequently, hinokiol was methylated and the resulting 12-methyl ether was dehydrated to afford 12-methoxyabieta-2,8,11,13-tetraene. The tetraene was then submitted to hydroboration-oxidation to give 12-methoxyabieta-8,11,13-trien-2α-ol (15) which, on demethylation with ethanethiol and anhydrous aluminium chloride, afforded salviol. Oxidation of 15 with pyridinium chlorochromate, followed by demethylation, gave 2-oxoferruginol.