1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 1 . 13 ( s , 6 H ) , 3 . 32 ( d , 2 H ) , 4 . 68 ( s , 1 H ) , 7 . 57 - 7 . 61 ( m , 2 H ) , 8 . 01 - 8 . 06 ( m , 2 H ) , 8 . 25 ( dt , 1 H ) , 8 . 68 ( s , 1 H ) , 8 . 76 ( d , 1 H ) , 8 . 87 ( t , 1 H ) , 9 . 45 ( t , 1 H ) .