Selective transmembrane carriers for hydroxycarboxylic acids: influence of a macrocyclic calix[4]arene platform

Selective transmembrane carriers for alpha-hydroxy acids, acyclic a-amino phosphonates and calix[4]arenes containing alpha-aminophosphonate substituents at the lower rim have been synthesized; analytical HPLC has been used to monitor the selective separation of dicarboxylic, alpha-hydroxy and alpha-amino acid mixtures by membrane extraction; the attachment of alpha-aminophosphonate fragments to the macrocyclic calix[4]arene platform results in receptors with markedly modified efficiency and selectivity relative to those of only aminophosphonates.