Synthesis and enantiomeric recognition studies of dialkyl-substituted 18-crown-6 ethers containing an acridine fluorophore unit

Synthesis, Molecular Recognition Study and Liquid Membrane-Based Applications of Highly Lipophilic Enantiopure Acridino-Crown Ethers

New highly lipophilic enantiopure crown ethers containing a heterocyclic unit have been synthesized. Phase transport, UV-Vis- and fluorescence spectrophotometric investigations as well as electrochemical studies on the complexation of the new macrocycles with several amine and amino acid derivatives were also carried out. Achiral amines were used for studying the structural preference of the new macrocycles. Among the studied structural features of the guest molecules, the intermolecular π-π interaction showed the most significant effect on complexation, which made the aralkylamine-type compounds the most preferable guest molecules. The studied liquid membrane-based applications and photophysical investigations showed appreciable enantiomeric recognition toward some aralkylamine model compounds with homochiral preferences. New crown ether derivatives (R,R)-2 and (S,S)-2 were successfully applied as enantioselective carrier and sensor molecules.

Optically active crown ether-based fluorescent sensor molecules: A mini-review

This mini-review focuses on fluorescent optically active crown ethers (polymeric derivatives are not included) reported in the literature (according to our knowledge), of which enantiomeric recognition ability, and in some cases, also inorganic cation complexation properties, were investigated by the sensitive and versatile fluorescence spectroscopy. These crown ether-based chemosensors contain various fluorophore signaling units such as binaphthyl, anthracene, pyrene, tryptophan, benzimidazole, terpyridine, acridine, phenazine, acridone, BODIPY, and another conjugated aromatic one.

Synthesis and pKa determination of new enantiopure dimethyl-substituted acridino-crown ethers containing a carboxyl group: Useful candidates for enantiomeric recognition studies

New enantiopure dimethyl-substituted acridino-18-crown-6 and acridino-21-crown-7 ethers containing a carboxyl group at position 9 of the acridine ring [(S,S)-8, (S,S)-9, (R,R)-10] were synthesized. The pK_a values of the new crown ethers [(S,S)-8, (S,S)-9, (R,R)-10] and of an earlier reported macrocycle [(R,R)-2] were determined by UV-pH titrations. Crown ether (S,S)-8 was attached to silica gel by covalent bonds and the enantiomeric separation ability of the newly prepared chiral stationary phase [(S,S)-CSP-12] was studied by high-performance liquid chromatography (HPLC). Homochiral preference was observed and the best separation was achieved for the enantiomers of 1-NEA. Ligands (S,S)-9 and (R,R)-10 are precursors of enantioselective sensor and selector molecules for the enantiomers of protonated primary amines, amino acids, and their derivatives.