1 H NMR ( 300 MHz , CDCl 3 ) δ : 8 . 45 ( d , J = 8 . 3 Hz , 1 H ) , 8 . 30 ( d , J = 8 . 3 Hz , 1 H ) , 7 . 73 - 7 . 61 ( m , 2 H ) , 6 . 90 ( s , 1 H ) , 5 . 39 - 5 . 30 ( m , 2 H ) , 4 . 03 ( s , 3 H ) , 3 . 97 ( s , 3 H ) , 1 . 52 ( d , J = 6 . 4 Hz , 6 H ) .