1 H NMR ( 400 MHz , DMSO - d 6 ) : δ ppm 12 . 09 ( s , 1 H ) , 10 . 11 ( s , 1 H ) , 8 . 18 ( s , 1 H ) , 8 . 09 ( d , J = 10 . 5 Hz , 1 H ) , 7 . 90 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 86 - 7 . 80 ( m , 1 H ) , 7 . 64 - 7 . 59 ( m , 1 H ) , 7 . 49 ( d , J = 7 . 6 Hz , 1 H ) , 6 . 54 ( s , 1 H ) , 4 . 22 ( s , 3 H ) . ( ESI ) : m / z 405 . 1 [ M + H ] +.