1 H NMR ( 400 MHz , DMSO - d 6 ) : δ 7 . 69 ( d , J = 5 . 2 Hz , 1 H ) , 7 . 07 ( d , J = 5 . 2 Hz , 1 H ) , 7 . 00 - 7 . 03 ( m , 2 H ) , 6 . 55 ( d , J = 2 . 4 Hz , 1 H ) , 6 . 44 ( dd , J = 8 . 4 , 2 . 4 Hz , 1 H ) , 4 . 44 ( d , J = 6 . 0 Hz , 2 H ) , 3 . 87 ( s , 3 H ) , 3 . 81 ( s , 3 H ) , 3 . 72 ( s , 3 H ) .