¹H NMR (700 MHz, DMSO) δ 12.30 (s, 1H), 10.59 (s, 1H), 7.56 (s, 2H), 7.30 (d, J = 7.0 Hz, 8H), 7.22 (t, J = 6.7 Hz, 2H), 6.46 (s, 2H), 3.59 (s, 5H).