Reaction Steps
As described for the synthesis of 3′,5′-bis-O-(tert-butyldimethylsilyl)-O6-(4-nitrophenyl)-2′-deoxyinosine, this 3-cyanophenyl derivative was prepared by a reaction between O6-(benzotriazol-1-yl)-3′,5′-bis-O-(tert-butyldimethylsilyl)-2′-deoxyinosine (26) (59.8 mg, 0.100 mmol) and 3-cyanophenol (13.1 mg, 0.110 mmol) in the presence of Cs2CO3 (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at 85° C. over 2 h. Chromatographic purification (SiO2, elution with 20% EtOAc in hexanes) afforded 47.5 mg (82% yield) of the title compound as a clear gum. Rf (50% EtOAc in hexanes)=0.58. 1H NMR (500 MHz, CDCl3): δ 8.49 (s, 1H, Ar—H), 8.45 (s, 1H, Ar—H), 7.62-7.54 (m, 4H, Ar—H), 6.54 (t, 1H, H-1′, J=6.4), 4.64 (m, 1H, H-3′), 4.05 (q, 1H, H-4′, J=3.4), 3.91 (dd, 1H, H-5′, J=11.2, 3.9), 3.80 (dd, 1H, H-5′, J=11.2, 3.9), 2.64 (app quint, 1H, H-2′, Japp˜6.3), 2.49 (ddd, 1H, H-2′, J=13.2, 6.3, 4.4), 0.92, 0.916 (2 s, 18H, tert-Bu), 0.11, 0.105 (2 s, 12H, SiCH3). 13C NMR (126 MHz, CDCl3): δ 159.1, 153.0, 152.7, 151.6, 142.2, 130.4, 129.2, 126.7, 125.6, 122.1, 117.9, 113.6, 88.1, 84.8, 71.8, 62.7, 41.5, 25.9, 25.7, 18.4, 17.9, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C29H44N5O4Si2 (M++H) 582.2932. found 582.2927.
