Cyclohexene → N2-isobutyryl-O6-diphenylcarbamoyl-3'-O-azidomethyl-2'-deoxyguanosine

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To 786 mg 12 (1.1 mmol) dissolved in 8 mL dry CH2Cl2 was treated with 0.56 mL cyclohexene and 180 μL SO2Cl2 (2.2 mmol) at 0° C. and stirred for 1.5 h at the same temperature. The solvent was then removed by rotary evaporation, and further dried under high vacuum for 10 minutes. The crude product was then dissolved in 5 mL dry DMF and reacted with 600 mg NaN3 (10 mmol) at 0° C. and stirred at room temperature for 3 h. Reaction mixture was then partitioned H2O/CH2Cl2, the combined organic extract was then dried over Na2SO4, and concentrated by rotary evaporation. The crude was then dissolved in 5 mL dry MeOH, treated with 500 mg NH4F (13.5 mmol) at room temperature for more than 24 h. Then MeOH solvent was removed by rotary evaporation, and partitioned (H2O/CH2Cl2). The combined organic part was dried over Na2SO4 and concentrated by rotary evaporation and purified by silica gel column chromatography resulting pure product of 14 as white powder (230 mg, ˜36% yield in three steps; hex: EtOAc 1:1 to 1:5, (Rf=˜0.3, Hex:EtOAc/1:4). HR-MS: Obs. m/z 588.2343, calcd for C28H30O6N9 588.2319 [M+H]+. 1H-NMR (DFM-d6): δH 8.64 (brs, 1H), 7.48-7.34 (m, 10H), 6.36 (t, J=7.0 Hz), 4.93 (m, 2H), 4.76 (m, 1H), 4.04 (m, 1H), 3.57 (m, 1H), 3.34 (m, 2H), 2.97 (m, 1H), 2.81 (m, 1H), and 1.10 (m, 6H).

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