Binding and Transport of Alkali and Alkaline Earth Metal Ions by Synthetic Macrolides Containing Tetrahydropyran Rings

Article abstract of DOI:10.1021/ja00404a020

Ion binding and transport abilities of 10-, 20-, and 25-membered macrolides (2, 4, and 5, respectively) consisting of alternating tetrahydropyran and ester moieties were evaluated mainly by extraction equilibrium and transport experiments of various metal picrates.The macrolide 2 was totally ineffective in ion binding and transport.The ion extraction constants of the macrotetrolide 4 and the macropentalide 5 were found to be in the order of ca. 10-10², and their ion selectivity sequences were Cs⁺ > Rb⁺ > K⁺ > Na⁺ > Li⁺ and Ba²⁺ > Ca²⁺.The transport rate of metal picrates mediated by 4 and 5 through organic liquid membranes decreased in the order, Cs⁺ > Rb⁺ > K⁺ > Ba²⁺ > Ca²⁺ ca.Na⁺ > Li⁺, the selectivity of K⁺ over Na⁺ being ca. 2-3.Separated measurements of ion uptake and ion release, along with the selectivity sequences above, suggested that the ion uptake step was rate determining in the transport of metal picrates by 4 and 5.These ion binding properties and transport behaviors are discussed in comparison with those of some natural and synthetic ionophores.