| 90% |
With trifluoroacetic acid In dichloromethane at 0 – 20℃; Darkness |
Trifluoroacetic acid (20 mL) was added dropwise to a solution of 11 (5 g, 14.3 mmol) in dichloromethane (60 mL) at 0 °C. The reaction mixture was warmed to room temperature and stirred for 2 h in dark. The solution was concentrated by evaporation and diluted by EA (150 mL). A saturated aqueous NaHCO3 solution was added slowly via a cannula at 0 °C until pH 7~8. The aqueous layer was extracted with EA (80 mL.x.2). The EA extract was washed with a saturated aqueous NaCl solution (150 mL), dried over Na2SO4 and evaporated under reduced pressure. The residue was purified by silica gel column chromatography (PE/EA 10:1) to give a white solid (3.2 g, 90percent yield). 1H NMR (400 MHz, CDCl3) 7.07 (t, J = 8.0 Hz, 1H), 6.42-6.40 (m, 1H), 6.24-6.21 (m, 1H), 4.22 (br, 2H), 3.85 (s, 3H). 13C NMR (100 MHz, CDCl3) 158.9, 148.4, 129.5, 107.8, 100.7, 76.0, 56.3. MS (ESI, m/z) found 250.0 ([M+H]+). |