Organosoluble calixarene-based quinolone carriers: syntheses, evaluation and model hydrolytic studies at the air–water interface

Two tetra-p-tert-butyl- and two tetra-p-H-calix[4]arene species integrating one or two propylnalidixate esters at the lower rim have been synthesized as possible antibacterial prodrugs. As they display amphiphilic behavior, their properties at the air–water interface were evaluated using the Langmuir balance technique. It has been shown that the two tert-butyl analogues form stable monolayers. The two tert-butyl analogues were then studied at 20 and 37 °C on carbonate buffered subphases at pH 10.0, before being engaged in hydrolytic studies on “production” of monolayers so as to allow a simple treatment, a HPLC survey of nalidixate release. The latter was found to be effective at 37 °C, with formation of free nalidixate in 13% yield for the bisnalidixate derivative, and 10% yield for the mononalidixate after 3 days.