1.58 g (5.86 mmol) of (RS)-1-(2-azido-propyl)-6-methoxy-1,4-dihydro-indeno[2,1-c]pyrazole dissolved in 50 ml of anhydrous ethanol were hydrogenated over 160 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 80 ml of anhydrous diethyl ether, filtered and treated while stirring with a solution of 680 mg (5.86 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. 1.81 g (86%) of (RS)-2-(6-methoxy-1,4-dihydroindeno[2,1-c]pyrazol-1-yl)-1-methyl-ethylamine fumarate (1:1) with m.p. 192°-194° were obtained.
