Relationships of the Enantioselective Retention of Chiral Oxazolopyrroloquinolones on a Stationary Phase with Grafted Antibiotic Ristocetin A

A study is performed of mechanisms of the retention and separation of enantiomers of a series of chiral oxazolopyrroloquinolones on a stationary phase with grafted macrocyclic antibiotic ristocetin A under the conditions of high-performance liquid chromatography using water–acetonitrile mobile phases. It is found that the dependence of the retention factor on the concentration of CH3CN in the mobile phase has a U-shape. An explanation of this phenomenon is given. The thermodynamics of the oxazolopyrroloquinolone adsorption in different parts of this dependence is studied. It is assumed that the adsorption complex forms through inclusion of the oxazole moiety of the adsorbate molecule in the chiral cavity of the grafted selector. The effect the nature of the substituent on the chiral carbon atom in oxazolopyrroloquinolones on enantioseparation is discussed.