A mixture of compound 207 (3.40 g, 8.54 mmol) and 4-methoxybenzylamine (11.2 mL, 85.4 mmol) in dry DMSO (22 mL) was stirred under a nitrogen atmosphere at 70° C. (bath temperature) for 138 h. The mixture was then cooled and poured into water (400 mL). Petroleum ether (400 mL) was added and stirred at room temperature for 30 min. The layers were allowed to separate and the petroleum ether layer was decanted. This procedure was repeated with more petroleum ether (400 mL). It was filtered and washed solid with water (3×30 mL). The sticky yellow/orange solid was stirred with acetone (100 mL) at room temperature for ca. 30 min. to give a fine orange precipitate. Water (200 mL) was added and stirred further at room temperature for 2 h. The solid was collected by suction-filtration, washed with water/acetone (2:1) (5×30 mL), and dried in vacuum over silica-gel/KOH to give pure N4-(3,4-dibromophenyl)-N6-(4-methoxybenzyl)pyrido[3,4-d]pyrimidine-4,6-diamine (216) (4.16 g, 95%) as a greenish yellow solid, mp 166-169° C.; 1H NMR δ [(CD3)2SO] 9.72 (s, 1H), 8.77 (s, 1H, 8.42 (s, 1H), 8.40 (br s, 1H), 7.89 (br d, J=7.7 Hz, 1H), 7.76 (d, J=8.7, Hz, 1H), 7.40-7.25 (m, 3H), 7.17 (s, 1H), 6.88 (br d, J=8.3 Hz, 2H), 4.49 (d, J=5.9 Hz, 2H), 3.71 (s, 3H). Anal. Calcd for C21H17Br2N5O.0.25hexane: C, 50.35; H, 3.85; N, 13.05%. Found C, 50.56; H, 3.54; N, 12.87%.
