To the solution of 3-(3-bromobenzyl)-9-pentyl-6,9-dihydro-5H-[1,2,4]triazolo[4,3-a]purin-5-one (210 mg, 0.50 mmol) in tetrahydrofuran (20 mL) was added N-bromosuccinimide (140 mg, 0.00076 mol). The mixture was stirred at 70° C. for 1 hour. The reaction mixture was concentrated and the residue was purified by preparative LCMS to yield the desired product (0.15 g, 60%). 1HNMR (300 MHz, d6-DMSO): δ 7.16 (d, J=8.3 Hz, 2H), 6.81 (d, J=8.3 Hz, 2H), 4.46 (s, 3H), 4.20 (t, J=7.2 Hz, 2H), 3.67 (s, 2H), 1.79 (m, 2H), 1.28 (m, 4H), 0.83 (m, 3H). LCMS calculated for C18H19Br2N6O (M+H): 493. Found: 493, 495 and 497.
