1 H NMR ( 500 MHz , DMSO - d 6 ) 10 . 40 ( NH , br s , 1 H ) , 7 . 92 ( d , J = 8 . 5 Hz , 2 H ) , 7 . 71 ( d , J = 8 . 5 Hz , 2 H ) , 3 . 82 ( s , 3 H ) , 3 . 67 ( s , 2 H ) , 2 . 75 ( sep , J = 7 . 0 Hz , 1 H ) , 1 . 05 ( d , J = 7 . 0 Hz , 6 H ) , MH + 264 .