The Synthesis of Ar-abietatrien-12,16-oxide and Its C-15 Epimer

Article abstract of DOI:10.1246/bcsj.60.2401

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.