1 H NMR ( 300 MHz , DMSO - d 6 ) δ : 11 . 07 ( br s , 1 H ) , 8 . 31 ( d , J = 7 . 9 Hz , 1 H ) , 7 . 93 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 77 ( d , J = 8 . 6 Hz , 1 H ) , 7 . 65 - 7 . 51 ( m , 3 H ) , 7 . 09 ( s , 1 H ) , 4 . 03 ( s , 3 H ) .