1 H NMR ( 400 MHz , CDCl 3 ) δ 7 . 51 ( d , J = 2 . 4 Hz , 2 H ) , 7 . 28 - 7 . 22 ( m , 2 H ) , 6 . 99 ( d , J = 8 . 7 Hz , 2 H ) , 4 . 13 ( s , 4 H ) , 1 . 68 ( p , J = 7 . 5 Hz , 2 H ) , 1 . 32 - 1 . 21 ( m , 30 H ) .