Compound 19 (45 mg, 0.1 mmol) and sodium methylsulfinate (41 mg, 0.4 mmol) were dissolved in 2 mL N-methylpyrrolidone. The mixture was under microwave irradiation for 30 minutes at 120° C. with the power of 100 watts. After completion of the reaction, the reaction mixture was poured into water, extracted for three times with ethyl acetate, and extracted for three times with dichloromethane. The organic layers were combined and dried over anhydrous sodium sulfate. The solvent was concentrated under reduced pressure to a small volume. The crude product was purified by a preparative plate (dichloromethane:methanol=6:1) to obtain 12 mg of white solid (28.0%). m.p. 143-144° C. 1H NMR (300 MHz, CDCl3): δ 8.32 (d, J=5.2 Hz, 1H), 8.29 (s, 1H), 7.63 (d, J=1.2 Hz, 1H), 7.50 (d, J=5.2 Hz, 2H), 6.78 (d, J=1.2 Hz, 1H), 4.34 (s, 2H), 4.11 (t, J=4.4 Hz, 4H), 3.88 (t, J=4.4 Hz, 4H), 3.66 (s, 2H), 2.78 (s, 3H), 2.36 (s, 6H). MS (EI) m/e (%): 429 (M+, 12).
