A solution of 0.6 ml methanesulphonyl chloride in 3 ml absolute dioxane is added dropwise to a solution of 2.1 g rac-cis-6-(4-aminophenyl)-8,9-dimethoxy-1,2,3,4,4a, 10b-hexahydro-2-methyl-benzo[c ][1,6]naphthyridine in 20 ml absolute pyridine, and the mixture is then stirred at 60° C. for a further 3 h. After cooling, the mixture is poured onto 100 ml of an ice/water mixture, rendered alkaline with dilute sodium hydroxide solution and extracted with n-butanol. After the n-butanol has been evaporated off, the residue which remains is extracted with methylene chloride and the organic phase is dried over sodium sulphate and then concentrated. 2.4 g of the title compound are obtained as the residue and are converted into the dihydrochloride with ethereal HCl, and the product is recrystallized from non-dried methanol. Yield: 2.3 g of the title compound as the dihydrochloride hydrate. M.p. 239°-240° C. (decomposition).
