Reaction Steps
700 mg (2.8 mmol) of (9aR*,9bR*,13aR*)-2,7-dioxo-1,4,5,7,9a, 10,11,12,13,13a-decahydro-2H-pyrrolo[2',1':3,4]pyrazino[2,1-i]indole, dissolved in 30 ml of tetrahydrofuran, are hydrogenated with hydrogen in the presence of 70 mg of PtO2 at room temperature under normal pressure until the absorption of hydrogen ceases. The catalyst is filtered off and the filtrate is concentrated by evaporation in vacuo. The resulting oil is crystallised from ethyl acetate. In this manner (9aR*,9bR*,13aR*)-2,7-dioxo-1,4,5,7,8,9,9a,10,11,12,13,13a-dodecahydro-2H-pyrrolo[2',1':3,4]pyrazino[2,1-i]indole of formula ##STR6## is obtained, that is to say the compound of formula I in which R1, R2, R3, R4, R5, R6 and R7 are each a hydrogen atom, m is 2, n is 1 and the chiral C-atoms 9a, 9b and 13a have the above relative configuration (each R*) (melting range: 135° to 136°). The mother liquor is concentrated by evaporation in vacuo and chromatographed on silica gel (0.040-0.063 mm) with trichloromethane and trichloromethane/methanol (99:1) as eluants. There is thus obtained (9aR*,9bS*,13aS*)-2,7-dioxo-1,4,5,7,8,9,9a,10,11,12,13,13a-dodecahydro-2H-pyrrolo[2',1':3,4]pyrazino[2,1-i]indole, which is stereoisomeric as regards the relative configuration of the 9a C-atom, in the form of an oil which is crystallised from ethyl acetate and then melts at 177°-179°.
