CATION-TRANSPORT ACROSS BULK LIQUID ORGANIC MEMBRANES WITH OLIGOMERS OF (R)-3-HYDROXYBUTANOIC ACID

Several oligomeric derivatives 1-5 of (R)-3-hydroxybutanoic acid and a cyclic trimer of (R)-3-hydroxypentanoic acid (6) were used as ionophores to transport potassium picrate across a bulk liquid CH2Cl2 membrane. Using the cyclic trimer 1 and an oligomer mixture of (R)-3-hydroxybutanoic acid, 5 (ca. 28-mer), for the transport. experiments, the alkali-metal ions from Li+ to Cs+ and the alkaline-ear-th-metal ions from Mg2+ to Ba2+ were also shown to be transported through the organic phase. Although a pronounced enhancement of the transport rates was observed in the presence of 3-hydroxyalkanoate oligomers, no special selectivity for one ion was detected. The ionophore properties of the investigated oligomers and oligolides derived from 3-hydroxybutanoic acid are compatible with the alleged role of oligo(3-hydroxybutanoate) (c-PHB; ca. 120-mer)as component of ion channels through cell membranes.