1H NMR (400 MHz, CDCl3): δ 8.02 (d, J = 8.1 Hz, 2H), 7.80 (d, J = 8.1 Hz, 2H), 7.11 (dd, J = 17.1, 10.6 Hz, 1H), 6.48 (d, J = 17.1 Hz, 1H), 6.05 (d, J = 10.6 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 189.8, 140.4, 132.5, 132.0, 131.7, 129.0, 117.9, 116.2.