Synthesis and biological activity of squaramido-tethered bisbenzimidazoles as synthetic anion transporters.

A series of squaramido-tethered bisbenzimidazoles were synthesized from the reaction of diethyl squarate with substituted 2-aminomethylbenzimidazoles. These conjugates exhibit moderate binding affinity toward chloride anions. They are able to facilitate the transmembrane transport of chloride anions most probably an anion exchange process, and tend to be more active at acidic pH than at physiological pH. The viability of these conjugates toward four selected solid tumor cell lines was evaluated using an MTT assay and the results suggest that some of these conjugates exhibit moderate cytotoxicity probably in an apoptotic fashion.