1 H NMR ( 500 MHz , DMSO - d 6 ) : δ ppm 11 . 75 ( s , 1 H ) , 9 . 99 ( s , 1 H ) , 8 . 18 ( s , 1 H ) , 8 . 03 ( d , J = 8 . 5 Hz ) , 7 . 86 - 7 . 84 ( m , 2 H ) , 7 . 37 - 7 . 34 ( m , 1 H ) , 7 . 17 ( d , J = 8 . 5 Hz , 1 H ) , 7 . 08 - 7 . 05 ( m , 1 H ) , 6 . 98 ( s , 1 H ) , 4 . 23 ( s , 3 H ) , 3 . 94 ( s , 3 H ) . ( ESI ) : m / z 349 . 1 [ M + H ] +.