1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 3 . 66 - 3 . 73 ( m , 1 H ) , 3 . 79 - 3 . 86 ( m , 1 H ) , 4 . 80 - 4 . 92 ( m , 1 H ) , 5 . 45 ( br s , 1 H ) , 7 . 58 - 7 . 62 ( m , 2 H ) , 8 . 03 - 8 . 07 ( m , 2 H ) , 8 . 26 ( ddd , 1 H ) , 8 . 74 ( s , 1 H ) , 8 . 77 ( d , 1 H ) , 8 . 86 ( t , 1 H ) , 9 . 90 ( d , 1 H ) .