N-protection of 4,4'-diamnostilbene-2,2'-disulfonic acid (I) with 9-fluorenylmethyl chloroformate (Fmoc-Cl) by means of Na2CO3 in dioxane yields Fmoc-protected derivative (II), which reacts with triisopropylorthoformate in refluxing dioxane to provide bis(isopropyl) ester (III). Removal of the Fmoc-protecting groups of (III) by means of piperidine in DMF affords diamino compound (IV), which is then condensed with acid chloride (V) by means of K2CO3 in THF to provide compound (VI) [acid chloride (V) can be obtained by first treatment of p-(methylsulfanyl)benzoic acid (VII) with morpholine (VIII) in chlorosulfonic acid to give (IX), followed by reaction with oxalyl chloride in THF/DMF]. Finally, the target compound is obtained by treatment of bis(isopropyl) ester (VI) with sodium iodide (NaI) in acetone.

N-protection of 4,4'-diamnostilbene-2,2'-disulfonic acid (I) with 9-fluorenylmethyl chloroformate (Fmoc-Cl) by means of Na2CO3 in dioxane yields Fmoc-protected derivative (II), which reacts with triisopropylorthoformate in refluxing dioxane to provide bis(isopropyl) ester (III). Removal of the Fmoc-protecting groups of (III) by means of piperidine in DMF affords diamino compound (IV), which is then condensed with acid chloride (V) by means of K2CO3 in THF to provide compound (VI) [acid chloride (V) can be obtained by first treatment of p-(methylsulfanyl)benzoic acid (VII) with morpholine (VIII) in chlorosulfonic acid to give (IX), followed by reaction with oxalyl chloride in THF/DMF]. Finally, the target compound is obtained by treatment of bis(isopropyl) ester (VI) with sodium iodide (NaI) in acetone.