1 H - NMR ( 250 MHz , CDCl 3 ) δ 7 . 32 ( d , 2 H , J = 8 . 52 Hz ) , 7 . 25 - 7 . 16 ( m , 5 H ) , 6 . 81 ( d , 2 H , J = 8 . 57 Hz ) , 5 . 22 ( dd , 1 H , J 1 = 4 . 72 Hz , J 2 = 7 . 87 Hz ) , 2 . 79 - 2 . 65 ( m , 2 H ) , 2 . 34 ( s , 3 H ) , 2 . 27 - 1 . 88 ( m , 2 H )