The product of Example 44 (2.7 g, 8 mmol) was dissolved in N,N-dimethylformamide, potassium carbonate (2.7 g, 20 mmol) and dimethylamine hydrochloride (0.7 g, 8 mmol) were added therein, and it was reacted at room temperature for 12 hours. After the reaction solution was poured into water, the aqueous phase was extracted with dichloromethane twice, then the organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, concentrated, and separated through silica gel column chromatography to give target 2.1 g, yield: 89%.
