1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 3 . 49 ( ddd , 1 H ) , 3 . 72 - 3 . 80 ( m , 1 H ) , 4 . 18 - 4 . 29 ( m , 1 H ) , 6 . 67 ( d , 1 H ) , 7 . 65 ( ddd , 1 H ) , 7 . 89 ( d , 2 H ) , 8 . 18 ( ddd , 1 H ) , 8 . 22 ( d , 2 H ) , 8 . 71 ( dd , 1 H ) , 8 . 76 ( s , 1 H ) , 8 . 93 ( d , 1 H ) , 9 . 59 ( t , 1 H ) .