1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 1 . 34 ( t , 3 H ) , 4 . 38 ( q , 2 H ) , 8 . 07 ( d , 1 H ) , 8 . 63 ( s , 1 H ) , 8 . 73 ( dd , 1 H ) , 9 . 19 ( s , 1 H ) , 9 . 42 ( d , 1 H ) , 9 . 64 ( s , 1 H ) .