A Novel Method for the Preparation of a Chiral Stationary Phase Containing an Enantiopure Acridino-18-Crown-6 Ether Selector

Abstract

This paper reports a novel method for the preparation of chiral stationary phases (CSPs) using an acridino-18-crown-6 ether selector as a model compound. Chiral stationary phase (R,R)-CSP- 2A: was obtained by in situ continuously recirculating the solution of carboxyl-substituted acridino-18-crown-6 ether (R,R)- 4: , dicyclohexylcarbodiimide and 3-(triethoxysilyl)propylamine through a high-performance liquid chromatography (HPLC) column containing blank silica gel in elevated pressure and temperature. The enantiomer separating ability of chiral stationary phase (R,R)-CSP- 2A: was investigated by HPLC using mixtures of enantiomers of 1-(1-naphthyl)ethylamine hydrogen perchlorate, 1-(2-naphthyl)ethylamine, 1-(4-bromophenyl)ethylamine and 1-(4-nitrophenyl)ethylamine hydrogen chloride. The best results were found for the separation of the mixtures of enantiomers of Br-PEA.

Synthesis and Fluorescence Spectroscopic Studies of Novel 9-phenylacridino-18-crown-6 Ether Type Sensor Molecules

“…It was found for the studied primary amines (PEA and 1-NEA) that in all cases the (S)-enantiomer formed a more stable complex with (R,R)-2 than the (R)-enantiomer, demonstrating the generally observed higher stability of heterochiral complexes [(R,R)-crown ether-(S)-ammonium salt] compared to that of homochiral complexes [(R,R)-crown ether-(R)-ammonium salt]. This behavior is in unison with the earlier observations using acridino-crown ether based sensors and selectors [16,24,25]. Kertész and coworkers showed [16] that in the case of PGME the homochiral complex had higher stability, which was also observed by us.…”

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

“…Crown ether ( S,S )‐ 13 was heated without purification with spherical HPLC‐quality silica gel in toluene to obtain ( S,S )‐CSP‐ 12 (Scheme ). This method was faster and it gave better yield then the procedure reported by us previously for the preparation of dimethyl‐substituted acridino‐18‐crown‐6 ether‐based CSPs …”

“…In the cases of PEA, PGME, and kynurenine, enantiomeric discrimination was not observed. The enantioseparation factors of the new chiral stationary phase ( S,S )‐CSP‐ 12 compared to the enantioseparation factors of the reported acridino‐crown ether–based CSPs [( R,R )‐CSP‐ 4 , ( R,R )‐CSP‐ 5 , [( R,R )‐CSP‐ 6 ] indicate worse separation and resolution factors for all of the studied analytes. These observations also suggest that the position of the chiral center is crucial for the degree of enantiomeric recognition.…”

“…One of the main factors that determines the enantiomeric recognition ability of these crown ethers, the π–π interaction, can be enhanced by incorporating a heterocyclic unit containing a more extended aromatic system into the macroring, such as an acridine unit . The tricyclic ring system also makes the crown ether framework more rigid, which may further improve selectivity.…”

Investigation of Novel Cinchona Alkaloid-based Zwitterionic Chiral Stationary Phases in Cation- and Zwitterion-Exchange Modes

“…interactions, Hbonding and steric effects π-electron donor π-electron acceptor/π-electron donor [30] anion- [31] , cation- [32] zwitterionicexchange [33] ionic interaction polysaccharidebased cellulose [34,35] π-π, dipole-dipole, Hbonding and steric effects amylose [36,37] macrocyclic antibiotic-based macrocyclic glycopeptide [38,39] ionic, H-bonding, hydrophobic, dipoledipole, π-π-interaction, steric effects inclusion complexes modified cyclodextrin [40,41] complexation-, ionic interaction and steric effects crown ethers [42,43] CSPs derived from synthetic polymers polymers including vinyl, aldehyde, isocyanide, and acetylene polymers, condensation polymers including polyamides and polyurethanes, or cross-linked gels [44,45] steric effects molecularly imprinted polymers synthetic antibodies, enzymes, nucleic acid, hormones or glycoproteins [46,47] steric effects…”