Reaction Steps
The sodium salt of 2-chloro-6-(2-propylimidazol-1-yl)purine (0.13 g, 0.5 mmol) in dried CH3CN (10 mL) was treated with 2-deoxy-3,5-di-O-(p-toluoyl)-α-D-erythro-pentofuranosyl chloride (0.30 g, 0.8 mmol) in CH2Cl2 (10 mL) by general method 2. No α-nucleoside was detected by 1H NMR. Column chromatography was performed twice (25 g silica gel, MeOH/CH2Cl2, 1:30, and EtOAc/hexanes, 1:1) to give 2-chloro-9-[2-deoxy-3,5-di-O-(p-toluoyl)-β-D-erythro-pentofuranosyl]-6-(2-propylimidazol-1-yl)purine (0.26 g, 83%), which was recrystallized (EtOAc) to give analytically pure material (0.17 g, 55%): mp 192-193° C.; UV (MeOH) max 220, 239, 287 nm (∈ 40 700, 38 300, 16 700), min 231, 265 nm (∈ 35 900, 10 300); 1H NMR (500 MHz, CDCl3) δ 8.52 (s, 1H), 8.27 (s, 1H), 8.00 (d, J=7.8 Hz, 211), 7.86 (d, J=7.8 Hz, 2H), 7.32 (d, J=7.8 Hz, 2H), 7.28 (d, J=7.8 Hz, 2H), 7.20 (s, 1H), 6.61 (t, J=7.1 Hz, 1H), 5.82-5.83 (m, 1H), 4.84-4.68 (m, 3H), 3.29 (t, J=7.8 Hz, 2H), 2.98-3.01 (m, 2H), 2.47 (s, 3H), 2.38 (s, 3H), 1.86 (sext, J=7.5 Hz, 2H), 1.07 (t, J=7.3 Hz, 3H); NOE difference: H1′ was irradiated, and enhancement of H4′ (small), H8 and H2′,2″ signals was observed; 13C NMR (125 MHz, CDCl3) δ 166.29, 166.23, 154.38, 153.42, 151.47, 148.18, 144.97, 144.65, 142.40, 130.12, 129.78, 129.61, 129.56, 129.20, 126.63, 126.44, 122.95, 120.57, 85.46, 83.82, 75.19, 64.12, 38.88, 33.12, 22.03, 21.91, 21.60, 14.25; HRMS m/z 637.1940 (MNa+[C32H31ClN6O5Na=637.1942]). Anal. Calcd for C32H31ClN6O5: C, 62.49; H, 5.08; N, 13.66. Found: C, 62.44; H, 5.18; N, 13.72.
