1H NMR (400 MHz, CDCl3) δ 10.37 (s, 1H), 9.27 (d, J = 9.1 Hz, 1H), 8.02 (d, J = 6.5 Hz, 2H), 7.77 (d, J = 9.1 Hz, 1H), 7.69 (d, J = 7.6 Hz, 2H), 7.57 (d, J = 7.1 Hz, 1H), 7.34 (d, J = 7.6 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ 192.93, 145.07, 137.95, 136.32, 133.21, 132.31, 131.94, 131.27, 130.93, 129.44, 128.51, 127.15, 127.06, 122.87, 122.03.