To a solution of 9 (1.46 g, 5.2 mmol) in CH2Cl2 (5 mL) was added trifluoroacetic acid (5 mL) at 0° C. The mixture was stirred at 0° C. for 15 min. After evaporation of the solvent in vacuo, CH2Cl2 (15 mL) and triethylamine (2 mL) were added, then a solution of 6 (1.44 g, 5.9 mmol) in THF (25 mL) was added at 0° C. The reaction mixture was stirred overnight at room temperature. The solvent was evaporated in vacuo, then ethyl acetate (150 mL) was added, washed with water (50 mL×2) and saturated NaCl (50 mL), and dried over Na2SO4. After evaporation of the ethyl acetate, the crude product was purified with ether to afford 1.7 g (84%) of 10 as a yellow solid, mp 204.5-205.9° C. 1H NMR (300 MHz, CDCl3) δ 8.94 (s, 1H), 7.77 (dd, J=8.25 Hz, J=2.1 Hz, 1H), 7.67 (s, 1H), 7.02 (t, J=8.7 Hz, 2H), 6.84 (d, J=8.1 Hz, 1H), 6.69 (t, J=7.2 Hz, 1H), 6.63 (d, J=7.8 Hz, 2H), 3.89 (m, 1H), 3.75-3.66 (m, 2H), 3.23 (m, 1H), 2.96 (m, 1H), 1.72 (m, 2H), 1.54-1.42 (m, 2H). LRMS (FAB) m/e: 387.1 (M+H, 100). Anal. Calcd for C19.N2O5S: C, 59.06, H, 4.70; N, 7.25. Found: C, 58.99, H, 4.74, N, 7.11.
