1H NMR (400 MHz, CDCl3): δ 7.82 (d, J = 7.9 Hz, 2H), 7.63 (d, J = 8.0 Hz, 2H), 7.11 (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 189.9, 135.9, 132.0, 131.9, 130.7, 130.2, 128.2.