1 H NMR ( 400 MHz , CDCl 3 ) δ 8 . 74 - 8 . 68 ( 1 H , m ) , 8 . 27 - 8 . 23 ( 1 H , m ) , 8 . 21 ( 1 H , d , J = 9 . 4 Hz ) , 8 . 03 - 7 . 96 ( 1 H , m ) , 7 . 55 - 7 . 49 ( 1 H , m ) , 6 . 54 ( 1 H , d , J = 9 . 4 Hz ) , 2 . 90 ( 6 H , br s ) ;