1H NMR (400 MHz, CDCl3) δ 7.54 (s, 1H), 7.33 (d, J = 7.6 Hz, 2H), 7.26 (s, 1H), 7.20 (d, J = 7.7 Hz, 2H), 7.10 (s, 1H), 6.94 (d, J = 7.7 Hz, 2H), 6.81 (d, J = 7.7 Hz, 2H), 3.95 (s, 3H), 3.86 (s, 3H), 3.79 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 196.05, 160.52, 159.17, 159.09, 153.94, 138.85, 133.20, 131.65, 131.12, 130.62, 130.04, 124.81, 123.28, 114.36, 113.72, 106.29, 89.93, 56.94, 55.34, 55.20.