1 H NMR ( 400 MHz , CD 3 OD ) δ 8 . 36 ( d , J = 2 . 2 Hz , 1 H ) , 8 . 17 ( d , J = 2 . 1 Hz , 1 H ) , 8 . 05 ( d , J = 2 . 4 Hz , 1 H ) , 8 . 03 - 7 . 98 ( m , 2 H ) , 7 . 87 ( s , 1 H ) , 7 . 79 ( d , J = 8 . 5 Hz , 1 H ) , 7 . 73 ( d , J = 8 . 5 Hz , 1 H ) , 3 . 75 ( s , 2 H ) , 3 . 08 ( s , 4 H ) , 2 . 73 ( s , 7 H ) . LR - MS ( ESI ) m / z 529 ( M + 1 ) .