Reaction Steps
To a stirred solution of 57 (875 mg; 1.90 mmol) in anhydrous THF (45 mL), 1 M TBAF in THF solution (2.09 mL; 2.09 mmol) was added and the reaction was stirred at room temperature for 1 h. After evaporation, the residue was dissolved in 7 M ammonia in methanol solution (34 mL). The mixture was then stirred in a sealed flask at 50° C. for 9 h. After evaporation, the residue was purified by flash column chromatography using CH3OH—CH2Cl2 (1:10) as the eluent to afford 58 as white solid (548 mg; 99% yield): 1H NMR (400 MHz, CD3OD) δ 8.30 (s, 1H, 2-H), 8.17 (s, 1H, 8-H), 6.38 (dd, J=5.8, 8.6 Hz, 1H, 1′-H), 5.91-6.01 (m, 1H, CH2CH═CH2), 5.30-5.37 (dm, J=17.3 Hz, 1H, one of CH2CH═CH2), 5.17-5.22 (dm, J=10.6 Hz, 1H, one of CH2CH═CH2), 4.36 (m, 1H, 3′-H), 4.21 (m, 1H, 4′-H), 4.04-4.15 (m, 2H, CH2CH═CH2), 3.85 (dd, J=3.2, 12.3 Hz, 1H, one of 5′-H), 3.74 (dd, J=3.2, 12.3 Hz, 1H, one of 5′-H), 2.75-2.83 (ddd, J=5.7, 8.6, 13.6 Hz, 1H, one of 2′-H), 2.52-2.58 (ddd, J=1.8, 5.8, 13.6 Hz, 1H, one of 2′-H); 13C NMR (100 MHz, CD3OD) δ 157.1, 153.1, 149.5, 141.2, 135.6, 120.6, 117.0, 87.5, 87.2, 80.9, 71.0, 63.9, 38.7; HRMS (FAB+) calcd for C13H18O3N5 (M+H+): 292.1410, found: 292.1426.
