1 H NMR ( 400 MHz , DMSO - d 6 ) : δ ppm 12 . 00 ( s , 1 H ) , 10 . 09 ( s , 1 H ) , 8 . 18 ( s , 1 H ) , 8 . 09 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 90 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 80 ( d , J = 8 . 1 Hz , 1 H ) , 7 . 62 - 7 . 47 ( m , 2 H ) , 6 . 57 ( s , 1 H ) , 4 . 23 ( s , 3 H ) , 2 . 75 ( q , J = 7 . 5 Hz , 2 H ) , 1 . 26 ( t , J = 7 . 6 Hz , 3 H ) . ( ESI ) : m / z 415 . 1 [ M + H ] +.