1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 1 . 19 ( d , 3 H ) , 3 . 43 - 3 . 52 ( m , 2 H ) , 3 . 93 ( s , 3 H ) , 4 . 01 - 4 . 11 ( m , 1 H ) , 4 . 97 ( t , 1 H ) , 7 . 90 ( d , 2 H ) , 8 . 13 ( s , 1 H ) , 8 . 30 ( d , 2 H ) , 8 . 58 ( s , 1 H ) , 8 . 65 ( s , 1 H ) , 9 . 52 ( d , 1 H ) .