3,3'-Thiodipropanoic Acid was used as a reactant to synthesize bis(phenylacetamidothiadiazolyl)ethyl sulfide analogs as glutaminase inhibitors and antitumor agents. 3,3-thiodipropionic acid can also be used as precursor substrate for synthesis of 3-mercaptopropionic acid (M257070) containing polythioesters.