Cholapod anion receptors

It is also possible to produce charged cholapods, typically using guanidinium or ammonium groups but also imidazolium and triazolium moieties. These charged systems have been employed as anion receptors, smart transfer agents, and membrane transport anionophores. 

Cholapods (Scheme 9.5) are receptors based on a steroid core that feature both electron-withdrawing substituents (to enhance anion-binding) and a C2o side chain (to increase solubility in organic solvents). As might be expected, the rigid backbone present in cholapods makes them potentially ideal scaffolds in that they possess a fixed inner cavity as well as conformational rigidity [16,56,57]. However, only a few... 

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