To a solution of 10 (193 mg, 0.5 mmol) in DMF (3 mL) was added 60% NaH (30 mg, 0.75 mmol) at room temperature. The mixture was stirred 15 min, then iodomethane (0.5 mL) was added. The mixture was stirred overnight at ambient temperature, then ether (75 mL) was added, washed with water (30 mL) and saturated NaCl (30 mL), and dried over Na2SO4. After evaporation of the solvent, the crude product was purified with ether to afford 85 mg (43%) of 11a as a yellow solid, mp 160.1-160.9° C. 1H NMR (300 MHz, CDCl3) δ 8.07 (dd, J=8.25 Hz, J=2.1 Hz, 1H), 8.01 (s, 11H), 7.25 (t, J=8.4 Hz, 2H), 6.92 (m, 3H), 6.81 (d, J=7.8 Hz, 2H), 4.15 (dd, J=9.0 Hz, J=2.7 Hz, 1H), 4.00 (m, 1H), 3.92 (m, 1H), 3.51 (m, 1H), 3.30 (m, 1H), 3.26 (s, 3H), 2.04 (m, 2H), 1.81 (m, 2H). Anal. Calcd for C20H20N2O5S: C, 59.99, H, 5.03; N, 7.00. Found: C, 59.80, H, 5.03; N, 6.91.
