Reaction Steps
As described for the synthesis of 1a, this compound was prepared by a reaction of O6-(benzotriazol-1H-yl)-3′,5′-di-O-(tert-butyldimethylsilyl)-2′-deoxyguanosine25 (5.0 g, 8.16 mmol), allyl alcohol (50 mL) and Cs2CO3 (5.64 g, 17.1 mmol). Chromatographic purification of the crude material on a silica gel column using 30% EtOAc in hexanes) afforded 3.71 g (87% yield) of 1b as a white foam. Rf (SiO2/40% EtOAc in hexanes)=0.60. 1H NMR (CDCl3): δ 7.93 (s, 1H, Ar—H), 6.34 (t, 1H, H-1′, J=6.5 Hz), 6.17-6.09 (m, 1H, ═CH), 5.43 (dd, 1H, ═CHtrans, J=1.4, 17.2 Hz), 5.27 (dd, 1H, ═CHcis, J=1.4, 10.4 Hz), 5.01 (d, 2H, OCH2, J=5.7 Hz), 4.94 (s, 1H, NH2), 4.66-4.58 (m, 1H, H-3′), 3.99 (app q, 1H, H-4′, Japp˜3.5 Hz), 3.83 (dd, 1H, H-5′, J=4.4, 11.2 Hz), 3.77 (dd, 1H, H-5′, J=3.4, 11.2 Hz), 2.57 (app quint, 1H, H-2′, Japp˜6.5 Hz), 2.37 (ddd, 1H, H-2′, J=4.0, 6.0, 13.0 Hz), 0.92 (s, 18H, t-Bu), 0.11 and 0.09 (2s, 12H, SiCH3). 13C NMR (CDCl3): δ 160.0, 159.2, 153.5, 137.8, 132.8, 118.4, 116.0, 87.8, 88.8, 72.1, 67.5, 63.0, 41.1, 26.1, 25.9, 18.6, 18.1, −4.4, −4.6, −5.2, −5.3. HRMS calculated for C25H46N5O4Si2 [M+H]+: 536.3083. found: 536.3093.
