Patent ID: 8871933

Claim:
A method for preparing (−)-trans-3-(5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1-yl)-4-(1H-indol-3-yl)pyrrolidine-2,5-dione, comprising: a. mixing (±)-trans-3-(5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1-yl)-4-(1H-indol-3-yl)pyrrolidine-2,5-dione with (1S,2S)-(+)-pseudoephedrine in a first solvent to form solid (−)-trans-3-(5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1-yl)-4-(1H-indol-3-yl)pyrrolidine-2,5-dione.(1S,2S)-(+)-pseudoephedrine; b. washing the (−)-trans-3-(5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1-yl)-4-(1H-indol-3-yl)pyrrolidine-2,5-dione.(1S,2S)-(+)-pseudoephedrine solid formed in step (a) with an aqueous mixture of the first solvent; c. reacting the (−)-trans-3-(5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1-yl)-4-(1H-indol-3-yl)pyrrolidine-2,5-dione.(1S,2S)-(+)-pseudoephedrine from step (b) with an acid in an organic solvent and isolating the organic layer of the resultant solution; d. washing the organic layer from step (c); e. adding a second solvent to the organic layer; f. concentrating the organic layer until the amount of the second solvent in the solution is less than 5%; and g. crystallizing from the organic layer in step (f) and drying the resultant (−)-trans-3-(5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1-yl)-4-(1H-indol-3-yl)pyrrolidine-2,5-dione solution under vacuum, thereby producing (−)-trans-3-(5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1-yl)-4-(1H-indol-3-yl)pyrrolidine-2,5-dione.