1 H NMR ( 400 MHz , DMSO ) δ 8 . 58 ( d , J = 2 . 9 Hz , 1 H ) , 8 . 33 ( d , J = 2 . 9 Hz , 1 H ) , 8 . 06 ( d , J = 3 . 1 Hz , 1 H ) , 7 . 95 - 7 . 83 ( m , 2 H ) , 7 . 64 - 7 . 49 ( m , 2 H ) , 7 . 31 ( d , J = 15 . 0 Hz , 1 H ) , 6 . 89 ( s , 2 H ) , 3 . 54 ( s , 2 H ) , 2 . 57 - 2 . 44 ( m , 4 H ) , 2 . 41 - 2 . 31 ( m , 4 H ) , 2 . 11 ( s , 3 H ) . LR - MS ( ESI ) m / z 553 ( M + 1 ) .