1H NMR (400 MHz, CDCl3) δ 10.40 (s, 1H), 9.08 (s, 1H), 7.90 (d, J = 7.1 Hz, 1H), 7.39 (d, J = 7.2 Hz, 1H), 7.20 (s, 1H), 7.05 (s, 1H), 6.94 (s, 2H), 2.54 (s, 3H), 2.37 (s, 6H), 2.03 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 193.42, 147.91, 144.19, 138.48, 137.41, 135.90, 135.23, 132.96, 132.90, 130.39, 129.80, 128.95, 127.59, 126.73, 122.28, 25.30, 21.83, 21.31.