Receptors 5-11, bearing guanidinium, carbamate and (in some cases) other functional groups, were synthesized from cholic acid 1. These cations were shown to extract chiral carboxylate anions from aqueous buffer into chloroform with significant enantioselectivities. The most successful receptors bore two carbamate substituents and achieved, in the best cases, ratios (:) of 7-10:1 for a series of five N-acetyl α-amino acids.

The cationic steroidal receptors 9 and 11 have been synthesized from cholic acid 3. Receptor 9 extracts N-acetyl-a-amino acids from aqueous media into chloroform with enantioselectivities (l :d) of 7 ± 10:1. The lipophilic variant 11 has been employed for the enantioselective transport of N-acetylphenylalanine, a) through dichloromethane (DCM) and dichloroethane (DCE) bulk liquid membranes (U-tube apparatus), and b) through 2.5 % (v/v) octanol/hexane via hollow fibre membrane contactors. Significant enantioselectivities and multiple turnovers were observed for both types of apparatus.

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