Compound I-26 was prepared by the method which was identical with that for preparing compound 19, wherein compound 20 (37 mg, 0.1 mmol) was used as the starting material. Light yellow solid (12 mg, 26.7%) were obtained by a preparative plate (dichloromethane:methanol=8:1). m.p. 238-240° C. 1H NMR (300 MHz, CDCl3): δ 8.20 (s, 1H), 8.19 (d, J=7.1 Hz, 1H), 7.60 (s, 1H), 7.47-7.38 (m, 2 H), 6.88 (s, 1H), 4.41 (s, 2H), 4.02 (br, s, 4H), 3.81 (t, J=4.4 Hz, 4H), 2.95 (s, 2H), 2.94 (s, 3H), 2.87 (s, 1H), 2.51 (s, 6H). MS (EI) m/e (%): 444 (M+, 16).
