1 H NMR ( 400 MHz ; DMSO ; Me 4 Si ) , δ ( ppm ) : 1 H NMR ( 400 MHz , dmso ) δ 10 . 49 ( s , 1 H ) , 8 . 67 ( s , 2 H ) , 7 . 53 ( d , J = 1 . 6 Hz , 1 H ) , 7 . 32 ( d , J = 50 . 0 Hz , 1 H ) , 7 . 03 ( dd , J = 8 . 3 , 1 . 6 Hz , 1 H ) , 6 . 91 ( d , J = 8 . 2 Hz , 1 H ) , 4 . 17 ( t , J = 6 . 2 Hz , 1 H ) , 3 . 68 ( s , 2 H ) , 3 . 02 ( qd , J = 14 . 2 , 6 . 4 Hz , 1 H ) .