Towards “drug-like” indole-based transmembrane anion transporters

A series of mono-ureas and mono-thioureas, some incorporating a trifluoromethyl group, have been synthesised and their ability to facilitate ion transport assessed using a combination of ion selective electrode and fluorescence techniques. Chloride/nitrate and chloride/bicarbonate antiport and HCl symport processes were examined using phospholipid vesicles as a model system. In general, the trifluoromethyl functionalised receptors showed greater transport activity than unfluorinated analogous systems, corresponding with increased clogP. The most active transporter facilitated chloride efflux from phospholipid vesicles at receptor to lipid ratios as low as 1 : 20 000. In addition, in vitro fluorescence and viability assays indicated that the most potent anion transporters induced apoptosis in human cancer cell lines.