1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 3 . 47 - 3 . 54 ( m , 2 H ) , 3 . 57 - 3 . 63 ( m , 2 H ) , 3 . 93 ( s , 3 H ) , 3 . 94 - 4 . 02 ( m , 1 H ) , 4 . 89 ( t , 2 H ) , 7 . 58 - 7 . 62 ( m , 2 H ) , 8 . 07 - 8 . 13 ( m , 3 H ) , 8 . 57 ( s , 1 H ) , 8 . 60 ( s , 1 H ) , 9 . 63 ( d , 1 H ) .