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Under the protection of N2, to a solution of 2′-O-benzylinosine (1.0 g, 2.79 mmol) in 10 mL pyridine was added 4,4′-dimethoxytrityl chloride (2.36 g, 6.98 mmol). The mixture was stirred at room temperature for 2 h. The reaction was diluted with 100 mL dichloromethane and quenched with 100 mL saturated NaHCO3 solution. After the aqueous layer was extracted with dichloromethane (100 mL) three times, the organic layers were combined and evaporated. The residue was purified by flash chromatography (gradient: hexane with EtOAc 0-45%, with 1% triethylamine in both hexane and EtOAc) to produce 1.80 g (2.72 mmol, 98%) product. LCMS: for C38H36N4O7 calculated 660.3. found 661.2 [M+H]+. 1H NMR (600 MHz, CD3CN) δ: 7.83 (s, 1H), 7.80 (s, 1H), 7.39 (m, 2H), 7.23 (m, 12H), 6.82 (m, 4H), 6.02 (d, J=5.0 Hz, 1H), 4.71 (d, J=12.2 Hz, 1H), 4.59 (d, J=12.2 Hz, 1H), 4.54 (dd, J=5.1, 5.1 Hz, 1H), 4.42 (dd, J=9.6, 4.8 Hz, 1H), 4.14 (dd, J=8.4, 4.2 Hz, 1H), 3.64 (m, 1H), 3.57 (m, 1H). 13C NMR (600 MHz, CD3CN) δ: 158.88, 156.87, 145.48, 145.18, 138.51, 136.09, 135.98, 130.23, 128.50, 128.24, 128.16, 128.08, 128.07, 128.04, 128.00, 127.08, 117.58, 117.08, 117.04, 113.264, 86.91, 84.49, 80.70, 7229, 69.84, 63.55, 62.88, 55.15, 52.76.

1. customquenched with 100 mL saturated NaHCO3 solution
2. extractionAfter the aqueous layer was extracted with dichloromethane (100 mL) three times
3. customevaporated
4. customThe residue was purified by flash chromatography (gradient