Studies on the syntheses of heterocyclic compounds. Part 875. The total stereoselective retro mass spectral synthesis of (±)-emetine

Abstract

Addition of 3,4-dihydro-6,7-dimethoxy-1-methylisoquinoline (5) to 3-methoxycarbonyl-1,6,7,11b-tetrahydro-9,10-dimethoxybenzo[a]quinolizin-4-one (4) produced 2-[3,4-dihydro-6,7-dimethoxy-1-isoquinolyl)methyl]-3-methoxycarbonyl-1,2,3,6,7,11b-hexahydro-9,10-dimethoxybenzo[a]quinolizin-4-one (6A). The same reaction of 3,4-dihydro-1-methyl-9H-pyrido[3,4-b]indole (15) with (4) afforded 2-(3,4-dihydro-9H-pyrido[3,4-b]-1-indolyl)methyl]-1,2,3,6,7,11b-hexahydro-9,10-dimethoxy-3-methoxycarbonylbenzo[a]quinolizin-4-one (16). The former Michael adduct (6A) was converted into (±)-emetine (1) in six steps.