1H NMR (400 MHz, CDCl3): δ 7.90 (d, J = 8.1 Hz, 2H), 7.46 (d, J = 8.1 Hz, 2H), 7.12 (dd, J = 17.1, 10.6 Hz, 1H), 6.45 (d, J = 17.1 Hz, 1H), 5.96 (d, J = 10.6 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 189.7, 139.5, 135.5, 131.9, 130.7, 130.1, 128.9.