1 H NMR ( 500 MHz , DMSO - d 6 ) : δ ppm 12 . 48 ( s , 1 H ) , 10 . 27 ( s , 1 H ) , 8 . 19 ( s , 1 H ) , 8 . 03 - 8 . 02 ( m , 2 H ) , 7 . 86 - 7 . 71 ( m , 3 H ) , 6 . 89 ( t , J = 54 . 5 Hz , 1 H ) , 4 . 22 ( s , 3 H ) . ( ESI ) : m / z 481 . 0 [ M + H ] +.