Reaction Steps
A solution of 9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-2,6-dichloropurine (0.45 g, 1.0 mmol) and 4,5-diphenylimidazole (2.21 g, 10 mmol) in DMF (15 mL) was stirred at 65° C. under N2 for 67 h (reaction almost complete, TLC). Volatiles were evaporated in vacuo, and the residue was chromatographed (MeOH/CH2Cl2, 1:90) to give 9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-2-chloro-6-(4,5-diphenylimidazol-1-yl)purine (0.53 g, 83%) and a mixture of 4,5-diphenylimidazole (19 mg) and the title compound (52 mg, 91% total). Recrystallization (iPrOH) gave 9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-2-chloro-6-(4,5-diphenylimidazol-1-yl)purine: mp 146-146.5° C.; UV (MeOH) max 279 nm (∈ 18 300), min 267 nm (∈ 16 800); 1H NMR (500 MHz, CDCl3) δ 9.03 (s, 1H), 8.22 (s, 1H), 7.55-7.57 (m, 2H), 7.35-7.40 (m, 4H), 7.21-7.27 (m, 4H), 6.21 (d, J=5.5 Hz, 1H), 5.80 (“t”, J=5.6 Hz, 1H), 5.58 (“t”, J=5.1 Hz, 1H), 4.41-4.48 (m, 3H), 2.16 (s, 31), 2.15 (s, 3H), 2.09 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 170.2, 169.5, 169.4, 154.3, 153.5, 147.4, 142.9, 140.5, 139.2, 133.5, 131.1, 131.0, 128.33, 128.28, 128.17, 127.5, 127.2, 124.1, 86.4, 80.7, 73.2, 70.5, 62.9, 20.8, 20.5, 20.4; HRMS m/z 631.1694 (MNa+[C31H28ClN6O7Na]=631.1708). Anal. Calcd for C31H28ClN6O7: C, 59.00; H, 4.31; N, 13.32. Found: C, 58.89; H, 4.45; N, 13.24.
