1H NMR (400 MHz, CDCl3): δ 7.66 (d, J = 4.3 Hz, 2H), 7.12 (t, J = 4.3 Hz, 1H), 5.75 (s, 1H), 5.70 (s, 1H), 2.48 (q, J = 7.4 Hz, 2H), 1.11 (t, J = 7.4 Hz, 3H). 13C NMR (100 MHz, CDCl3): δ 190.1, 150.0, 143.8, 133.9, 133.9, 127.8, 121.3, 25.6, 12.3.