Reaction Steps
In a clean, dry reaction vial equipped with a stirring bar were placed O6-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (63.2 mg, 0.106 mmol), Cs2CO3 (68.9 mg, 0.211 mmol) and phenol (19.9 mg, 0.211 mmol). Dry toluene (1.0 mL) was added and the reaction mixture was flushed with N2 and the mixture was allowed to stir at 105° C. for 2 h. The reaction mixture was filtered through Celite, the residue washed with Et2O and the filtrate evaporated to dryness. Chromatographic purification (SiO2, elution with 20% EtOAc in hexanes) afforded 50.5 mg (86% yield) of the title compound as a clear gum. Rf (20% EtOAc in hexanes)=0.21. 1H NMR (500 MHz, CDCl3): δ 8.49 (s, 1H, Ar—H), 8.40 (s, 1H, Ar—H), 7.45 (app t, 2H, Ar—H, Japp˜7.8), 7.29-7.26 (m, 3H, Ar—H), 6.53 (t, 1H, H-1′, J=6.3), 4.64 (m, 1H, H-3′), 4.04 (q, 1H, H-4′, J=3.4), 3.90 (dd, 1H, H-5′, J=11.2, 3.9), 3.70 (dd, 1H, H-5′, J=11.2, 2.7), 2.65 (app quint, 1H, H-2′, Japp˜6.3), 2.48 (ddd, 1H, H-2′, J=13.2, 6.1, 4.1), 0.92, 0.91 (2 s, 18H, tert-Bu), 0.10 (s, 12H, SiCH3). 13C NMR (126 MHz, CDCl3): δ 160.2, 152.5, 152.4, 152.0, 141.6, 129.6, 125.7, 122.1, 121.9, 88.0, 84.6, 71.8, 62.7, 41.5, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C28H45N4O4Si2 (M++H) 557.2979. found 557.2978.
