1 H NMR ( CD 3 OD , 400 MHz ) δ 8 . 22 ( s , 1 H ) , 8 . 04 ( s , 1 H ) , 7 . 99 ( d , J = 9 . 7 Hz , 1 H ) , 7 . 51 - 7 . 43 ( m , 4 H ) , 7 . 32 - 7 . 29 ( m , 2 H ) , 7 . 24 ( t , J = 8 . 6 Hz , 2 H ) , 7 . 14 ( t , J = 8 . 6 Hz , 2 H ) , 7 . 07 ( d , J = 8 . 6 Hz , 2 H ) , 6 . 98 ( dd , J = 2 . 6 Hz , 9 . 7 Hz , 1 H ) , 6 . 38 ( d , J = 2 . 6 Hz , 1 H ) , 3 . 13 ( s , 6 H ) , 2 . 96 ( s , 6 H ) , 2 . 41 ( s , 3 H ) .