1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 3 . 44 - 3 . 52 ( m , 2 H ) , 3 . 55 - 3 . 62 ( m , 2 H ) , 3 . 92 - 4 . 01 ( m , 1 H ) , 4 . 88 ( t , 2 H ) , 7 . 57 - 7 . 62 ( m , 2 H ) , 8 . 01 - 8 . 05 ( m , 2 H ) , 8 . 25 ( br d , 1 H ) , 8 . 69 ( s , 1 H ) , 8 . 79 ( br s , 1 H ) , 8 . 87 ( br s , 1 H ) , 9 . 45 ( d , 1 H ) .