To a solution of 6-(4-hydroxy-phenyl)-1-(tetrahydro-pyran-2-yl)-3-vinyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid (3.12 g, 6.62 mmol) in tetrahydrofuran (44 mL) were added 1-boc-piperazine (1.35 g, 7.28 mmol), 1-hydroxybenzotriazole (0.09 g, 0.66 mmol), and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (1.27 g, 6.62 mmol). After 2 hours, N,N-dimethylacetamide (3 ml), 1-boc-piperazine (0.24 g, 1.32 mmol) and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (0.25 g, 1.32 mmol) were added to the reaction mixture. After 1 hour, tetrahydrofuran was evaporated under reduced pressure, water and dichloromethane were then added. The organic layer was washed with an aqueous 1M HCl solution, water, brine, dried (Na2SO4), filtered, concentrated under vacuum. The crude residue was purified on a silica gel column chromatography using a gradient of methanol (0-5%) in dichloromethane to yield the title compound as a yellow foam (3.17 g, 90%).
