A mixture of 1-[1-(4-fluorophenethyl)piperidin-4-yl]-6-(3-bromopropionylamino)methylindole (150 mg) obtained in Example 377, a 2 M solution (5.0 ml) of dimethylamine in tetrahydrofuran and toluene (5 ml) was heated at 80 to 90° C. for 1.5 days. Then water and ethyl acetate were added to the reaction mixtures. The organic layer was separated, washed with brine, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The resulting residue was purified by Chromatorex NH-silica gel column chromatography (hexane/ethyl acetate system) to give the title compound (140 mg) as an oil. This oil was crystallized from ethyl acetate by using oxalic acid (28 mg) to give the oxalate (110 mg) of the title compound as a white powder (yield: 66%).
