1 H NMR ( 500 MHz , DMSO - d 6 ) : δ ppm 12 . 18 ( s , 1 H ) , 10 . 13 ( s , 1 H ) , 8 . 19 ( s , 1 H ) , 8 . 14 ( d , J = 8 . 5 Hz , 1 H ) , 7 . 93 ( d , J = 8 . 5 Hz , 1 H ) , 7 . 84 - 7 . 81 ( m , 2 H ) , 7 . 67 - 7 . 65 ( m , 1 H ) , 7 . 17 ( t , J = 54 . 5 Hz , 1 H ) , 6 . 67 ( s , 1 H ) , 4 . 22 ( s , 3 H ) . ( ESI ) : m / z 403 . 1 [ M + H ] +.