1 H NMR ( 300 MHz , DMSO - d 6 ) δ : 7 . 99 ( d , J = 7 . 7 Hz , 1 H ) , 7 . 68 - 7 . 60 ( m , 5 H ) , 7 . 54 - 7 . 43 ( m , 2 H ) , 6 . 71 ( d , J = 7 . 5 Hz , 1 H ) , 4 . 30 ( t , J = 6 . 6 Hz , 2 H ) , 1 . 78 - 1 . 62 ( m , 3 H ) , 0 . 92 ( d , J = 6 . 4 Hz , 6 H ) .