1 H NMR ( 400 MHz , DMSO - d 6 ) : δ ppm 12 . 16 ( s , 1 H ) , 10 . 13 ( s , 1 H ) , 8 . 19 ( s , 1 H ) , 8 . 14 ( d , J = 8 . 8 Hz , 1 H ) , 7 . 93 - 7 . 91 ( m , 1 H ) , 7 . 88 - 7 . 81 ( m , 2 H ) , 7 . 17 ( t , J = 54 Hz , 1 H ) , 6 . 65 ( s , 1 H ) , 4 . 22 ( s , 3 H ) . ( ESI ) : m / z 405 . 1 [ M + H ] +.