To a solution of the compound obtained in Example 2 (300 mg) in dimethylformamide (3 ml) are added 2-picolyl chloride hydrochloride (118 mg) and potassium carbonate (182 mg), and the mixture is stirred at 50° C. overnight. To the mixture are added ethyl acetate and water. The ethyl acetate layer is separated, washed, dried, and concentrated under reduced pressure. The residue (chemical name; 6-methoxy-3-methoxycarbonyl-2-morpholino-7-(2-pyridylmethyloxy)-4-(3,4,5-trimethoxyphenyl-1(2H)-isoquinolinone) is dissolved in ethyl acetate, and thereto is added a 4M solution of hydrogen chloride in ethyl acetate (150 μl). The mixture is stirred at room temperature for 30 minutes. The precipitated crystals are collected by filtration, and washed with ethyl acetate to give 6-methoxy-3-methoxycarbonyl-2-morpholino-7-(2-pyridylmethyloxy)-4-(3,4,5-trimethoxyphenyl)-1(2H)-isoquinolinone hydrochloride (279 mg) as listed in Table 1.
