M-chloroperbenzoic acid (>65%) (796 mg) was added to a toluene (20 mL) solution of 2-allyl-6-(methylthio)-1-pyridin-2-yl-3H-pyrazolo[3,4-d]pyrimidin-3-one (898 mg), and stirred for 30 minutes. N,N-diisopropylethylamine (1.60 mL), [5-amino-2-(4-methylpiperazin-1-yl)phenyl]methanol (800 mg) and tetrahydrofuran (10 mL) were added to the reaction liquid, and stirred overnight. Aqueous saturated sodium hydrogencarbonate solution was added to the reaction liquid, and extracted with a chloroform/isopropanol (80/20) mixed solution. This was dried with anhydrous magnesium sulfate, the solvent was evaporated away, and the residue was purified through basic silica gel chromatography (hexane/ethyl acetate=50/50 to 0/100). The resulting crystal was recrystallized with ethanol to give the entitled compound as a white crystal (941 mg).
