Reaction Steps
N-Butyryl-5′-O-monomethoxytrityl-2′-O-methyladenosine 7 (100 mg, 0.16 mmol) was dried by evaporation of added dry pyridine (5 mL) under reduced pressure and finally by keeping on a vacuum pump for 30 min. Dry pyridine was added (2 mL) and the solution was put into ice-bath whereupon benzoyl chloride was added (1.2 eq, 0.19 mmol, 22.2 μL) and after 10 min the ice-bath was removed and the reaction was allowed to warm up and was then left stirring overnight at room temperature. A small amount of NaHCO3 (aq. sat.) was added and the solvent was evaporated under reduced pressure. Dichloromethane was added and the organic phase was washed with NaHCO3 (aq. sat. 2×). The organic phase was collected, dried (MgSO4), filtered and concentrated. Evaporation of added toluene (2×) and dichloromethane (2×) was done to remove traces of pyridine. The remaining crude material of compound 8 was dissolved in 80% acetic acid (10 mL) and allowed to react at room temperature for 4 h. after which deprotection of 5′-monomethoxytrityl was complete (TLC, mass). The solution was concentrated and added toluene (2×) and dichloromethane (2×) evaporated under reduced pressure to remove excess acetic acid. The compound was purified on silica gel column chromatography using a gradient of methanol in dichloromethane (0-5%). Yield 80% of compound 9. 1H NMR (CDCl3) δ 1.04 (3H, t, J=7.4 Hz), 1.80 (2H, m), 2.92 (2H, t, J=7.4 Hz), 3.31 (3H, s), 3.96 (2H, m), 4.51 (1H, s), 4.87 (1H, m), 5.90 (1H, d, J=4.9 Hz), 6.01 (1H, d, J=7.9 Hz), 6.32 (1H, d, J=9.9 Hz), 7.27 (2H, m), 7.51 (1H, m), 8.12 (2H, m), 8.18 (1H, s), 8.70 (1H, s), 9.27 (1H, s), 13C NMR δ 13.9, 18.4, 40.0, 59.3, 63.1, 72.7, 77.4, 81.4, 86.8, 89.9, 123.7, 128.1, 128.9, 129.8, 133.7, 143.5, 150.2, 152.1, 165.8, 173.5, MS (ES-TOF) m/z calculated: 455.18. found: 455.38.
