Reaction Steps
To a stirred solution of 19 (601 mg; 1.18 mmol) in anhydrous THF (28 mL), 1 M TBAF in THF solution (1.31 mL; 1.31 mmol) was added and the reaction mixture was stirred at room temperature for 1 h. After evaporation, the residue was dissolved in ethyl acetate (100 mL). The solution was then washed with saturated aqueous NaCl and dried over anhydrous Na2SO4. After evaporation, the residue was purified by flash column chromatography using CH3OH—CH2Cl2 (1:10) as the eluent to afford 20 as white crystals (329 mg; 71% yield): 1H NMR (400 MHz, CD3OD) δ 8.47 (s, 1H, 6-H), 6.15 (dd, J=6.2, 6.7 Hz, 1H, 1′-H), 5.87-5.98 (m, 1H, CH2CH═CH2), 5.26-5.33 (dm, J=17.2 Hz, 1H, one of CH2CH═CH2), 5.14-5.19 (dm, J=10.5 Hz, 1H, one of CH2CH═CH2), 4.18 (m, 1H, 3′-H), 4.08 (m, 1H, 4′-H), 3.98-4.10 (m, 2H, CH2CH═CH2), 3.82 (dd, J=3.2, 13.0 Hz, 1H, one of 5′-H), 3.72 (dd, J=3.3, 13.0 Hz, 1H, one of 5′-H), 2.44-2.51 (ddd, J=3.2, 6.0, 13.6 Hz, 1H, one of 2′-H), 2.07-2.15 (m, 1H, one of 2′-H); 13C NMR (100 MHz, CD3OD) δ 165.4, 156.9, 148.8, 135.6, 117.0, 87.9, 86.9, 79.6, 71.2, 62.7, 57.2, 39.7; HRMS (FAB+) calcd for C32H37O4N3I (M+H+): 394.0264, found: 394.0274.
