In a dried reaction flask, the crude 2-(3-chloro-4-cyanophenyl)-3-cyclopentyl-3,3a,4,5-tetrahydro-2H-pyrazolo[3,4-f]quinoline-7-carboxylic acid (Compound 1) (0.4 g, about 0.9 mmol), piperidine (0.18 mL, 1.818 mmol), DIEA (0.18 mL, 1.04 mmol) and HATU (0.342 g, 0.9 mmol) were added to a mixed solvent of DMF (4.5 mL) and dichloromethane (4.5 mL). The mixture was stirred at room temperature for 3 hr. Water was added. The mixture was filtered to obtain a crude yellow solid, which was washed with methanol to produce a purified product (0.375 g) in 85.4% yield.
