1 H NMR ( 500 MHz , DMSO - d 6 ) : δ ppm 11 . 92 ( s , 1 H ) , 10 . 01 ( s , 1 H ) , 8 . 18 ( s , 1 H ) , 8 . 05 ( d , J = 8 . 5 Hz , 1 H ) , 7 . 87 ( d , J = 8 . 5 Hz , 1 H ) , 7 . 61 - 7 . 59 ( m , 1 H ) , 7 . 28 - 7 . 25 ( m , 2 H ) , 6 . 69 ( s , 1 H ) , 4 . 23 ( s , 3 H ) , 3 . 15 - 3 . 12 ( m , 2 H ) , 2 . 96 - 2 . 93 ( m , 2 H ) , 2 . 10 - 2 . 04 ( m , 2 H ) . ( ESI ) : m / z 359 . 2 [ M + H ] +.