4-Amino-5-(phenylsulfonyloxy)naphthalene-2,7-disulfonic acid?diazo, and Naphthalen-1-amine coupling, its product to diazo, and 8-Aminonaphthalene-2-sulfonic acid coupling, again diazo, in alkaline conditions and 4-Hydroxy-7-(phenylamino)naphthalene-2-sulfonic acid coupling, and then hydrolysis benzene acyl sulfonylurea medications.