To a solution of 2-(biphenyl-4-ylmethyl)-7-(4-methoxybenzyl)-5-methyl-2H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione (300 mg, 0.663 mmol) in THF (9 mL), a solution of ammonium cerium (IV) nitrate (1.82 g, 3.32 mmol) in water (3 mL) is added. The resulting orange solution is stirred at room temperature overnight. Another batch of CAN (1.82 g, 3.32 mmol) is added and the mixture is stirred for 6 hours, and then the third batch of CAN (1.82 g) is added, and the mixture is stirred at r.t. overnight. The reaction mixture is evaporated to dryness. The residue is treated with brine, and extracted with methylene chloride five times. The organic phase is combined and concentrated. The residue is purified by chromatography to give product as white solids with a high yield. 1H NMR (400 MHz, DMDO-d6) δ 3.16 (s, 3H), 5.37 (s, 2H), 7.38 (m, 3H), 7.46 (m, 2H), 7.65 (m, 4H), 8.59 (s, 1H), 11.6 (s, 1H). MS (FAB) m/z 333.3 [M+H]+.
