1 H NMR ( 400 MHz , DMSO - d 6 ) δ = 10 . 52 ( s , 1 H ) , 9 . 04 ( t , J = 6 . 4 Hz , 1 H ) , 7 . 99 ( d , J = 8 . 8 Hz , 2 H ) , 7 . 76 ( d , J = 8 . 8 Hz , 2 H ) , 7 . 68 ( d , J = 4 . 0 Hz , 1 H ) , 7 . 15 ( d , J = 4 . 0 Hz , 1 H ) , 4 . 88 - 4 . 84 ( m , 1 H ) , 4 . 20 ( m , 1 H ) , 3 . 94 ( s , 4 H ) , 3 . 92 - 3 . 88 ( m , 1 H ) , 3 . 58 - 3 . 56 ( m , 2 H )