5-(4-Chloro-phenyl)-6-(2,4-dichloro-phenyl)-1-(4-nitro-phenyl)-1,5-dihydro-pyrazolo[3,4-d]pyrimidin-4-one (100 mg, 0.195 mmol) is dissolved in 20 mL of dioxane. Platinumoxide (11.0 mg, 0.0484 mmol) was added as a slurry in 2 mL of water to the reaction mixture under a nitrogen atmosphere. The mixture was placed under balloon pressure of hydrogen and the reaction is completed within 1 h. The solids are filtered off and the solution is concentrated. Purification by reverse phase HPLC affords the title compound. 1H NMR (DMSO, 400 MHz) δ 8.78 (s, 1H), 8.15 (d, 2H), 7.97-7.95 (m, 2H), 7.90 (m, 3H), 7.84 (dd, 1H), 7.78 (m, 1H), 7.30 (d, 2H), 6.00 (s, 2H). HPLC-MS calculated for C23H14Cl3N5O (M+H+) 482.0. Found: 482.0.
