1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 3 . 48 ( ddd , 1 H ) , 3 . 75 ( ddd , 1 H ) , 4 . 17 - 4 . 28 ( m , 1 H ) , 6 . 67 ( br s , 1 H ) , 7 . 57 - 7 . 61 ( m , 2 H ) , 7 . 64 ( ddd , 1 H ) , 7 . 99 - 8 . 04 ( m , 2 H ) , 8 . 17 ( ddd , 1 H ) , 8 . 67 - 8 . 71 ( m , 2 H ) , 8 . 92 ( d , 1 H ) , 9 . 61 ( t , 1 H ) .