Reaction Steps
In a 50 mL round-bottomed flask equipped with a stirring bar were placed 2′-deoxyinosine 24 (0.504 g, 2.00 mmol) and BOP (1.770 g, 4.00 mmol). DMF (20 mL) and DIPEA (0.70 mL, 4.00 mmol) were added and the mixture was allowed to stir at room temperature for 26 h. The reaction mixture was evaporated with toluene several times. The crude product was dissolved in EtOAc and washed with water. The organic layer was separated, dried over Na2SO4 and concentrated. Chromatographic purification (SiO2, elution with 10% MeOH in CH2Cl2) afforded 0.421 g (57% yield) of compound 28 as a pale brownish-white foam. Rf (10% MeOH in CH2Cl2)=0.38. 1H NMR (500 MHz, CDCl3): δ 8.43 (s, 1H, Ar—H), 8.24 (s, 1H, Ar—H), 8.16-8.14 (m, 1H, Ar—H), 7.57-7.54 (m, 1H, Ar—H), 7.49-7.46 (m, 1H, Ar—H), 6.46 (dd, 1H, H-1′, J=9.2, 5.5), 5.10 (dd, 1H, OH, J=11.3, 2.3, CD3OD exchangeable), 4.83 (br m, 1H, H-3′), 4.25 (br s, 1H, H-4′), 3.97 (dt, 1H, H-5′, J=12.8, 2.0), 3.82 (app td, 1H, H-5′, Japp˜11.9, 1.8), 3.07 (ddd, 1H, H-2′, J=13.4, 9.5, 4.9), 2.42 (dd, 1H, H-2′, J=13.6, 5.7), 2.05 (d, 1H, OH, CD3OD exchangeable). 13C NMR (126 MHz, DMSO-d6): δ 159.1, 153.1, 151.1, 144.8, 143.2, 129.1, 128.8, 125.2, 120.5, 120.3, 108.7, 88.9, 86.9, 72.2, 62.7, 40.9. FAB HRMS calcd for C16H16N7O4 (M++H) 370.1264. found 370.1258.
