Revision of Structures of Nellionol and Dehydronellionol

Abstract The structures of nellionol and dehydronellionol were revised respectively to 6α,11,12,16-tetrahydroxyabieta-8,11,13-trien-7-one (12) and 6,11,12,16-tetrahydroxyabieta-5,8,11,13-tetraen-7-one (13) by the following syntheses. A mixture of (15R)- and (15S)-12-methoxyabieta-8,11,13-trien-16-ol, prepared from 13-acetyl-12-methoxypodocarpa-8,11,13-triene, was converted into 11,12,16-triacetoxyabieta-8,11,13-trien-7-one (22) via 16-acetoxy-12-benzoyloxyabieta-8,11,13-trien-11-ol. Treatment of 22 with isopropenyl acetate, followed by oxidation with m-chloroperbenzoic acid and subsequent acetylation, afforded 6α, 11,12,16-tetraacetoxyabieta-8,11,13-trien-7-one, which was hydrolyzed with dilute hydrochloric acid to 12. The ketone 22 was also converted into 13 via 11,12,16-triacetoxyabieta-8,11,13-trien-6-one. The spectral data of 12 and 13 were in good agreement with those of natural nellionol and dehydronellionol.