Aqueous NaOH (0.308 g, 7.72 mmol) was added to a solution of ethyl 6-bromo-1-cyclopentyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylate (1.3 g, 3.8 mmol) in EtOH (10 mL) and stirred at 60° C. for 1 h. After completion of the reaction, ethanol was removed under reduced pressure and it was acidified using 10% citric acid solution. Extraction was carried out using ethyl acetate; the combined organic layers were washed with water, brine and dried over anhydrous Na2SO4; filtered and concentrated under reduced pressure. The crude acid (1 g, 3.23 mmol) was then dissolved in DMSO (10 mL) and 3-(aminomethyl)-4,6-dimethylpyridin-2(1H)-one (0.98 g, 6.47 mmol) was added to it. The reaction mixture was stirred at room temperature for 15 min before PYBOP (2.52 g, 4.85 mmol) was added to it and stirring was continued overnight. After completion of the reaction, reaction mass was poured into ice to obtain solid, which was filtered and washed with acetonitrile followed by ether to provide the desired intermediate (1 g, 70%).
