1 H NMR ( DMSO - d 6 , 400 MHz ) : δ ppm 8 . 18 ( s , 1 H ) , 8 . 07 ( d , J = 8 . 8 Hz , 1 H ) , 8 . 00 - 7 . 96 ( m , 4 H ) , 7 . 88 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 06 ( s , 1 H ) , 4 . 22 ( s , 3 H ) . ( ESI ) : m / z 363 . 1 [ M + H ] +.