1H NMR (400 MHz, CDCl3) δ 10.36 (s, 1H), 9.27 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 7.2 Hz, 1H), 7.74 (s, 1H), 7.58 (d, J = 9.0 Hz, 1H), 7.54 (d, J = 7.3 Hz, 1H), 7.40 (d, J = 8.8 Hz, 4H), 2.58 (s, 3H), 2.46 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 193.23, 145.60, 139.04, 138.08, 136.20, 135.36, 132.47, 130.60, 130.12, 128.78, 128.01, 126.76, 126.25, 125.45, 122.03, 15.59, 15.46.