1 H - NMR ( 400 MHz , CDCl 3 ) δ : 7 . 55 ( 2 H , s ) , 7 . 05 ( 1 H , t , J = 7 . 6 Hz ) , 6 . 94 ( 1 H , d , J = 7 . 6 Hz ) , 6 . 89 ( 2 H , s ) , 6 . 70 ( 1 H , d , J = 8 . 8 Hz ) , 4 . 57 ( 2 H , t , J = 9 . 2 Hz ) , 3 . 96 ( 2 H , d , J = 5 . 6 Hz ) , 3 . 12 ( 2 H , t , J = 8 . 8 Hz ) , 2 . 18 ( 3 H , s ) .