General Conjugate-Addition Method for the Synthesis of Enantiomerically Pure Lignans. Total Synthesis of (-)- and (+)-Burseran, (-)-Dehydroxycubebin, (-)-Trichostin, (-)-Cubebin, (-)-5''-Methoxyhinokinin, and (-)-Hinokinin

Article abstract of DOI:10.1021/jo00301a026

Conjugate addition of benzylic diphenyldithioacetal anions to enantiomerically pure (-)-(2R)-and (+)-(2S)-(benzyloxy)-2,5-dihydro-4-<3,4-(methylenedioxy)benzoyl>furan (2 r and 2 s) gave complete lignan skeletons of the dibenzylbutane class.Desulfurization followed by hydrogenolysis and, when appropriate, oxidation gave the title enantiomerically pure > 99 percent ee) lignans 45 - 50 in 24 - 35 percent overall yields from 2 r and 2 s.