1 H NMR ( 400 MHz , DMSO - d 6 ) δ 10 . 47 ( s , 1 H ) , 8 . 29 ( s , 1 H ) , 8 . 03 ( d , J = 2 . 4 Hz , 1 H ) , 7 . 64 ( d , J = 1 . 6 Hz , 1 H ) , 7 . 51 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 26 - 7 . 28 ( m , 1 H ) , 7 . 26 ( dd , J = 1 . 6 , 8 . 8 Hz , 1 H ) , 7 . 03 - 7 . 07 ( m , 3 H ) , 6 . 96 - 7 . 00 ( m , 2 H ) , 6 . 81 - 6 . 83 ( m , 2 H ) , 6 . 60 - 6 . 64 ( m , 2 H ) , 6 . 41 ( s , 1 H ) , 3 . 63 ( s , 2 H ) .