1 H NMR ( 400 MHz , CD 3 OD ) δ 8 . 39 ( s , 1 H ) , 8 . 26 ( s , 1 H ) , 7 . 99 ( s , 1 H ) , 7 . 81 ( s , 1 H ) , 7 . 49 ( d , J = 9 . 9 Hz , 2 H ) , 7 . 31 ( s , 1 H ) , 4 . 71 ( s , 2 H ) , 3 . 51 ( s , 2 H ) , 2 . 81 ( s , 1 H ) , 2 . 46 ( s , 3 H ) , 2 . 32 ( s , 3 H ) , 2 . 12 ( s , 3 H ) . LR - MS ( ESI ) m / z 525 ( M + 1 ) .