The Total Synthesis of (15R)- and (15S)-16-Hydroxyferruginol

Article abstract of DOI:10.1246/bcsj.58.340

In order to assign the absolute configuration of C-15 in natural 16-hydroxyferruginol, (5S,10S,15R)-(1a) and (5S,10S,15S)-8,11,13-abietatriene-12-16-diol (1b) have been synthesized.Optical resolution of 2-(2-methoxyphenyl)propanoic acid, prepared from methyl (2-methoxyphenyl)acetate, with cinchonidine afforded (R)- and (S)-enantiomers, which were converted into <(R)-4-methoxy-3-(2-methoxy-1-methylethyl)benzyl>triphenylphosphonium chloride (3a) and its (S)-isomer (3b) respectively.The Wittig reaction of (R)-(-)-α-cyclocitral with 3a, followed by partial catalytic hydrogenation and intramolecular cyclization gave (5S,10S,15R)-12,16-dimethoxy-8,11,13-abietatriene (16a) together with its (5S,10R,15R)-isomer.Similary, 3b was also converted into (5S,10S,15S)-12,13-dimethoxy-8,11-abietatriene (6b) and its (5S,10R,15R)-isomer.Demethylation of 16a gave 1a which was identical with natural 16-hydroxyferruginol.The dimethoxy compound 16b was also demethylated to give 1b.