1 H NMR ( DMSO - d 6 , 400 MHz ) : δ ppm 12 . 27 ( s , 1 H ) , 10 . 05 ( s , 1 H ) , 8 . 49 ( s , 1 H ) , 8 . 19 ( s , 1 H ) , 8 . 13 ( d , J = 7 . 6 Hz , 1 H ) , 8 . 05 ( d , J = 8 . 8 Hz , 1 H ) , 7 . 91 - 7 . 87 ( m , 2 H ) , 7 . 57 ( dd , J 1 = J 2 = 7 . 6 Hz , 1 H ) , 7 . 01 ( s , 1 H ) , 4 . 22 ( s , 3 H ) . ( ESI ) : m / z 363 . 0 [ M + H ] +.