Total synthesis of the lignans (-)- and (+)-burseran, (-)-cubebin, and (-)-hinokinin by diastereoselective conjugate addition of benzyl anions to 2-(R) and (s)-benzyloxy-2,5-dihydro-4-(3,4-methylenedioxybenzoyl)furan
1,2-Addition of 3,4-methylenedioxymagnesium bromide to 2-(R) and (S)-benzyloxy-2,5-dihydro-4-furancarboxaldehyde, followed by oxidation, gave the title ketones (3r and 3s). Conjugate addition of the anions of 3,4,5-trimethoxy- and 3,4-methylenedioxybenzaldehyde diphenylthioacetal to 3r and 3s and Raney-nickel desulfurisation, followed by hydrogenolysis under various conditions, gave the title lign
