Into a 100-mL round-bottom flask, was placed a solution of 3-ethyl-1-phenyl-6-(piperidin-4-yl)-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-one hydrochloride (200 mg, 0.56 mmol, 1.00 equiv) in N,N-dimethylformamide (40 mL) at room temperature. To the resulting mixture was then added 4-bromopyridine hydrochloride (131 mg, 0.68 mmol, 1.10 equiv), in portions at room temperature, followed by triethylamine (188 mg, 1.86 mmol, 3.00 equiv), in portions at room temperature. The resulting solution was stirred overnight at 130° C. The resulting mixture was concentrated under vacuum. The resulting residue (150 mg) was purified by Prep-HPLC with the following conditions (Gilson Pre-HPLC): Column, SHISEIDO, CAPCELL PAK C18, 20 mm ID*250 mm, 5 u; mobile phase, methanol/H2O; Detector, UV 254 nm, to yield 3-ethyl-1-phenyl-6-(3,4,5,6-tetrahydro-2H-[1,4′]bipyridinyl-4-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-ol as a white solid.
