0.85 g (3.2 mmol) of (RS)-1-(2-azido-propyl)-7-methoxy-1,4-dihydro-indeno[2,1-c]pyrazole dissolved in 50 ml of anhydrous ethanol was hydrogenated on 85 mg of platinum oxide for 2 hours. The catalyst was subsequently filtered off, rinsed with ethanol and the solvent was removed in a vacuum. The colorless oil obtained was dissolved in 70 ml of anhydrous diethyl ether, filtered and treated while stirring with a solution of 371 mg (3.2 mmol) of fumaric acid in 10 ml of methanol. The mixture was stirred at room temperature for 15 hours and the white crystals were subsequently filtered off. 0.9 g (78%) of (RS)-2-(7-methoxy-1,4-dihydro-indeno[2,1-c]pyrazol-1-yl)-1-methyl-ethylamine fumarate (1:1) with m.p. 182° was obtained.
