The condensation of 1-benzoyl-1,2,2a,3,4,5-hexahydrobenzo[c,d]indol-4-one (I) with methylamine followed by acylation of the resulting enamine with benzoyl chloride gives 1,N-dibenzoyl-4-(methylamino)-1,2,2a,3-tetrahydrobenzo[c,d]indole (II) which, by irradiation with UV light in acetone, is isomerized to (5aR*,6aS*,12bS*)-4-benzoyl-7-methyl-4,5,5a,6,6a,7,8,12b-octahydroindolo[4,3-ab]phenanthridin-8-one (III). The reduction of (III) with LiAlH4 in ether, followed by hydrolysis with NaOH, and optical resolution with (+)-mandelic acid affords (+)-(5aS,6aR,12bR)-7-methyl-4,5,5a,6,6a,7,8,12b-octahydroindolo[4,3-ab]phenanthridine (IV), which is finally dehydrogenated with MnO2 in methylene chloride.

The condensation of 1-benzoyl-1,2,2a,3,4,5-hexahydrobenzo[c,d]indol-4-one (I) with methylamine followed by acylation of the resulting enamine with benzoyl chloride gives 1,N-dibenzoyl-4-(methylamino)-1,2,2a,3-tetrahydrobenzo[c,d]indole (II) which, by irradiation with UV light in acetone, is isomerized to (5aR*,6aS*,12bS*)-4-benzoyl-7-methyl-4,5,5a,6,6a,7,8,12b-octahydroindolo[4,3-ab]phenanthridin-8-one (III). The reduction of (III) with LiAlH4 in ether, followed by hydrolysis with NaOH, and optical resolution with (+)-mandelic acid affords (+)-(5aS,6aR,12bR)-7-methyl-4,5,5a,6,6a,7,8,12b-octahydroindolo[4,3-ab]phenanthridine (IV), which is finally dehydrogenated with MnO2 in methylene chloride.