The conversion of racemic α-cyclocitral into 3-(3-isopropyl-4-methoxyphenethyl)-4,4-dimethyl-2-methylenecyclohexanone (2) was carried out in five steps via 3-(3-isopropyl-4-methoxyphenethyl)-2,4,4-trimethyl-1-cyclohexene. An intramolecular cyclization of 2 with polyphosphoric acid produced the corresponding two tricyclic ketones possessing cis- and trans-A/B ring junctions. Each of these ketones was further converted into 12-mesyloxy-9(10→20)-abeo-abieta-1(10),8,11,13-tetraene in four steps. The mesylate was reduced with lithium aluminium hydride to give (±)-pisiferin.

In order to elucidate the absolute configuration of C-15 in natural ar-abietatrien-12,16-oxide, (15R)-12,16-epoxy-8,11,13-abietatriene (1a) and its (15S)-epimer (1b) have been synthesized. Treatment of (15R)-8,11,13-abietatriene-12,16-diol with a mixture of chloromethyl methyl ether, dicyclohexano-18-crown-6, and potassium carbonate afforded 1a as a minor product and (15R)-12-methoxymethyl ether as a major product. The latter was further converted into 1a. A similar treatment of (15S)-8,11,13-abietatriene-12,16-diol gave 1b. Catalytic hydrogenations of 12,16-epoxy-8,11,13,15-abietatetraene, methyl 12,16-epoxy-8,11,13,15-abietatetraen-19-oate (5), and methyl 12,16-epoxy-8,11,13,15-abietatetraen-18-oate (7) afforded the corresponding (15R)-dihydrobenzofuran derivatives and their (15S)-epimers. Conversions of the hydrogenation products from 5 and 7 into 1a and 1b were also carried out. The synthetic 1a was identical with natural ar-abietatrien-12,16-oxide.

To determine the absolute configurations of C-15 in natural nellionol and 5-dehydronellionol, (15R)-8,11,13-abietatriene-12,16-diol was converted into (15R)-6α,11,12,16-tetrahydroxy-8,11,13-abietatrien-7-one (3a) and (15R)-6,11,12,16-tetrahydroxy-5,8,11,13-abietatetraen-7-one (4a), which were identical with natural products. For direct comparisons with 3a and 4a, (15S)-6α,11,12,16-tetrahydroxy-8,11,13-abietatrien-7-one (3b) and (15S)-6,11,12,16-tetrahydroxy-5,8,11,13-abietatetraen-7-one (4b) were also synthesized from (15S)-8,11,13-abietatriene-12,16-diol. The synthetic 3b and 4b were not identical with the natural products. From the present study, the absolute configurations of nellionol and 5-dehydronellionol were conclusively assigned as 5S,6R,10S,15R (3a) and 10R,15R (4a), respectively.

A resin acid, (+)-dehydroabietic acid, was converted into 3,4,4a,9,10,10a-hexahydro-7-methoxy-10aβ-methyl-4aαH-phenanthren-1(2H)-one (2) by the introduction of oxygen functions at the C-4 and C-13 positions, and a rearrangement of the angular methyl group to the C-5 position. The hydrophenanthrene derivative 2 was further transformed into 2,3,3a,4,5,9b-hexahydro-7-methoxy-3aβ-methyl-9bαH-1H-benz[e]inden-3β-ol (3). Since the conversion of 3 into steroidal hormones has already been reported, the present synthesis can be regarded as the synthesis of steroidal hormones from (+)-dehydroabietic acid.

In order to elucidate the absolute configuration of C-15 in natural lycoxanthol, (15R)-11,16-dihydroxy-12-methoxymethoxy-8,11,13-abietatrien-7-one and its (15S)-epimer were transformed into (15R)-12,16-epoxy-6,11,14-trihydroxy-5,8,11,13-abietatetraen-7-one (1a) and its (15S)-epimer, respectively. The synthetic 1a was identical with natural lycoxanthol. Thus, the stereochemistry of C-15 in the natural compound was conclusively assigned as R-configuration.