1 H NMR ( 400 MHz , DMSO - d 6 ) δ : 11 . 79 ( s , 1 H ) , 10 . 82 ( s , 1 H ) , 8 . 18 - 8 . 16 ( m , 2 H ) , 7 . 87 - 7 . 79 ( m , 1 H ) , 7 . 79 - 7 . 65 ( m , 2 H ) , 7 . 64 - 7 . 54 ( m , 2 H ) , 7 . 50 ( d , J = 8 . 6 Hz , 1 H ) , 6 . 90 ( t , J = 54 . 8 Hz , 1 H ) , 4 . 21 ( s , 3 H ) . MS ( ESI ) : m / z 402 . 0 [ M + H ] +.