Reaction Steps
As described for the synthesis of 6-(morpholin-4-yl)-9-[2-deoxy-3,5-bis-O-(tert-butyldimethylsilyl)-β-D-erythro-pentofuranosyl]purine, this benzyl derivative was prepared by a reaction between O6-(benzotriazol-1-yl)-2′,3′,5′-tris-O-(tert-butyldimethylsilyl)inosine (27) (71.8 mg, 0.099 mmol) and benzylamine (21.8 μL, 0.200 mmol) in the presence of Cs2CO3 (65.2 mg, 0.200 mmol) in dry DME (1.0 mL) at room temperature over 7 h. Chromatographic purification (SiO2, elution with 3% EtOAc in hexanes followed by 20% EtOAc in hexanes) afforded 61.0 mg (87% yield) of the title compound as a clear gum. Rf (20% EtOAc in hexanes)=0.39. 1H NMR (500 MHz, CDCl3): δ 8.40 (s, 1H, Ar—H), 8.09 (s, 1H, Ar—H), 7.38 (d, 2H, Ar—H, J=7.3), 7.34 (t, 2H, Ar—H, J˜7.3), 7.28 (app t, 1H, Ar—H, Japp˜8.5), 6.02 (d, 1H, H-1′, J=5.4), 5.95 (br s, 1H, NH), 4.86 (br s, 2H, CH2), 4.70 (t, 1H, H-2′, J=4.9), 4.32 (t, 1H, H-3′, J=3.9), 4.12 (q, 1H, H-4′, J=3.4), 4.03 (dd, 1H, H-5′, J=11.2, 4.1), 3.78 (dd, 1H, H-5′, J=11.2, 2.9), 0.95, 0.93, 0.80 (3 s, 27H, tert-Bu), 0.13, 0.12, 0.11, 0.10, −0.04, −0.22 (6 s, 18H, SiCH3). 13C NMR (126 MHz, CDCl3): δ 154.7, 153.0, 149.4, 139.1, 138.6, 128.6, 127.7, 127.4, 120.4, 88.4, 85.4, 75.6, 72.1, 62.6, 44.8, 26.0, 25.8, 25.7, 18.4, 18.0, 17.8, −4.4, −4.7, −5.1, −5.4.
