1H NMR (400 MHz, CDCl3) δ 10.28 (s, 1H), 8.92 (s, 1H), 7.85 (d, J = 7.4 Hz, 1H), 7.44 (d, J = 7.4 Hz, 1H), 7.32 (s, 1H), 7.05 (d, J = 11.0 Hz, 3H), 4.09 (s, 3H), 3.98 (s, 3H), 3.91 (s, 3H), 3.83 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 193.98, 151.86, 149.58, 148.88, 148.78, 145.63, 135.71, 132.87, 128.88, 128.22, 127.42, 124.51, 121.95, 112.76, 111.15, 105.34, 104.39, 56.06, 56.00, 55.96, 55.59.