δ [ ppm ] = 1 . 16 ( d , 3 H ) , 2 . 31 ( s , 3 H ) , 3 . 40 - 3 . 49 ( m , 2 H ) , 3 . 97 - 1 H NMR ( 400 MHz , DMSO - d 6 ) : 4 . 08 ( m , 1 H ) , 4 . 93 ( t , 1 H ) , 6 . 33 ( d , 1 H ) , 7 . 55 - 7 . 60 ( m , 2 H ) , 7 . 95 ( d , 2 H ) , 8 . 61 ( s , 1 H ) , 9 . 45 ( d , 1 H ) , 12 . 85 ( s , 1 H ) .