1 H NMR ( 400 MHz , DMSO - d 6 ) δ 8 . 882 ( t , J = 5 . 6 Hz , 1 H ) , 7 . 74 ( dd , J = 12 . 4 , 2 . 0 Hz , 1 H ) , 7 . 71 ( t , J = 8 . 0 Hz , 1 H ) , 7 . 63 ( d , J = 4 . 0 Hz , 1 H ) , 7 . 43 ( dd , J = 8 . 8 , 1 . 6 Hz , 1 H ) , 6 . 96 ( d , J = 4 . 0 Hz , 1 H ) , 4 . 96 - 4 . 89 ( m , 1 H ) , 4 . 20 ( t , J = 8 . 8 Hz , 1 H ) , 3 . 66 ( dd , J = 9 . 2 , 6 . 4 Hz , 1 H ) , 3 . 74 - 3 . 63 ( m , 2 H )