Reaction Steps
As described for the synthesis of 3′,5-bis-O-(tert-butyldimethylsilyl)-O6-methyl-2′-deoxyinosine, the allyl 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 allyl alcohol (1 mL) in the presence of Cs2CO3 (65.2 mg, 0.200 mmol) over 2 h. Chromatographic purification (SiO2, elution with 20% EtOAc in hexanes) afforded 46.4 mg (89% yield) of the title compound as a clear gum. Rf (20% EtOAc in hexanes)=0.29. 1H NMR (500 MHz, CDCl3): δ 8.51 (s, 1H, Ar—H), 8.27 (s, 1H, Ar—H), 6.50 (t, 1H, H-1′, J=6.4), 6.16 (m, 1H, —CH═), 5.45 (dd, 1H, ═CHtrans, J=17.1, 1.5), 5.29 (d, 1H, ═CHcis, J=10.7), 5.12 (d, 2H, OCH2, J=5.4), 4.61 (m, 1H, H-3′), 4.02 (q, 1H, H-4′, J=3.4), 3.87 (dd, 1H, H-5′, J=11.2, 3.9), 3.77 (dd, 1H, H-5′, J=11.2, 2.9), 2.61 (app quint, 1H, H-2′, Japp˜6.3), 2.44 (ddd, 1H, H-2′, J=12.9, 6.1, 3.9), 0.91 (s, 18H, tert-Bu), 0.09, 0.08 (2 s, 12H, SiCH3). 13C NMR (126 MHz, CDCl3): δ 160.3, 151.9, 151.6, 140.6, 132.4, 121.9, 118.5, 87.9, 84.4, 71.8, 67.5, 62.7, 41.4, 26.0, 25.7, 18.4, 18.0, −4.7, −4.8, −5.4, −5.5. FAB HRMS calcd for C25H45N4O4Si2 (M++H) 521.2979. found 521.2974.
