Reaction Steps
In a clean, dry reaction vial equipped with a stirring bar were placed O6-(benzotriazol-1-yl)-2′,3′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol), Cs2CO3 (65.2 mg, 0.200 mmol) and imidazole (13.6 mg, 0.200 mmol). Dry DME (1.0 mL) was added and the reaction mixture was flushed with N2 and the mixture was allowed to stir at 85° C. for 4 h. The reaction mixture was concentrated and the residue was dissolved in EtOAc. The mixture was washed with water, dried over Na2SO4, and evaporated to dryness. Chromatographic purification (SiO2, elution with 50% EtOAc in hexanes) afforded 32.0 mg (60% yield) of the title compound as a clear gum. Rf (20% EtOAc in hexanes)=0.07. 1H NMR (500 MHz, CDCl3): δ 9.19 (s, 1H, Ar—H), 8.77 (s, 1H, Ar—H), 8.48 (s, 1H, Ar—H), 8.40 (s, 1H, Ar—H), 7.25 (s, 1H, Ar—H), 6.56 (t, 1H, H-1′, J=6.3), 4.64 (app q, 1H, H-3′, Japp˜4.2), 4.06 (m, 1H, H-4′), 3.90 (dd, 1H, J=11.2, 3.9), 3.80 (dd, 1H, H-5′, J=11.2, 2.9), 2.65 (app quint, 1H, H-2′, Japp˜6.3), 2.51 (m, 1H, H-2′), 0.92, 0.915 (2 s, 18H, tert-Bu), 0.11, 0.10 (2 s, 12H, SiCH3). 13C NMR (126 MHz, CDCl3): δ 153.0, 152.1, 145.6, 143.0, 137.7, 130.6, 122.9, 117.3, 88.1, 84.7, 71.7, 62.6, 41.5, 25.9, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5.
