Enantiomeric Recognition Ability Research Articles

Fluorescence and Circular Dichroism Dual-Mode Probe for Chiral Recognition of Tyrosine and Its Applications in Bioimaging.

Chiral amino acids (AAs) are essential in metabolism and understanding physiological processes, and they could be used as biomarkers for the diagnosis of different diseases. In this study, chiral Cdots@Van were prepared by postmodifying an achiral Cdots core with vancomycin for recognizing and determining the enantiomeric excess (ee) of tyrosine (Tyr) enantiomers. The fluorescence response of Cdots@Van is based on an "on-off" strategy, with different quenching percentages for d- and l-tyrosine. Interestingly, the circular dichroism (CD) spectrum of Cdots@Van responded to only one form of Tyr enantiomer, specifically d-Tyr, and remained nearly unchanged upon the addition of l-Tyr. Quantum mechanical (QM) calculations were in excellent agreement with the experimental results, confirming the stronger binding affinity of Cdots@Van for d-Tyr compared to l-Tyr. We further investigated the chiral recognition ability of the interconnected vancomycin particles, which was synthesized using the EDC/NHS coupling reaction between vancomycin molecules without a Cdots core. Surprisingly, unlike free vancomycin molecules, interconnected vancomycin displayed an enantiomeric recognition ability by CD spectroscopy, similar to what was observed for Cdots@Van. Crucially, this chiral probe has been successfully utilized for cell imaging applications.

Larger Groups, Smaller Enantioselectivity? Two Anthracene-Containing, Pyridino-Crown Ether-Based Fluorescent Sensor Molecules

(R,R)- and (S,S)-enantiomers of anthracene-containing pyridino-18-crown-6 ether having tert-butyl groups at the stereogenic centers were prepared with the aim of achieving higher enantioselectivity than for the reported (S,S)-analogue having isobutyl groups. The enantiomeric recognition abilities of the new sensor molecules toward chiral protonated primary amines and amino acid esters were studied in acetonitrile by UV–vis and fluorescence spectroscopies. The pKa values of these pyridino-crown ethers and their reported (S,S)-analogues having methyl or isobutyl groups have also been determined in acetonitrile.

Construction of cellulose-based highly sensitive extended-gate field effect chiral sensor.

Chiral recognition is an emerging field of modern chemical analysis, and the development of health-related fields depends on the production of enantiomers. Cellulose is a kind of natural polymer material with certain chiral recognition ability. Limited by the chiral recognition ability of natural cellulose itself, more cellulose derivatives have been gradually developed for chiral recognition and separation. Based on the difference in action between cellulose derivatives and enantiomers, this work synthesized cellulose-tris(4-methylphenylcarbamate) (CMPC) chiral recognition mediators and a CMPC-functionalized extended-gate organic field effect transistor (EG-OFET) was constructed for the first time. Three chiral molecules were selected as model analytes to evaluate the enantiomeric recognition ability of the platform, including threonine (Thr), 2-chloromandelic acid (CA), and 1,2-diphenylethylenediamine (DPEA). The detection limit for 1,2-diphenylethylenediamine (DPEA) is down to 10-13M. Through the amplification effect of the EG-OFET platform, the difference in the interaction between CMPC and three chiral molecules with different structures is converted into a current signal output. At the same time, the enantiomer discrimination mechanism of CMPC was further studied by means of spectroscopy and nuclear magnetic resonance.

Synthesis and Enantiomeric Recognition Studies of Novel C2-Symmetrical Chiral Tetra-Amide Compounds

Two novel C2-symmetrical chiral tetraamide compounds derived from (S)-isoleucine were synthesised and their enantiomeric recognition abilities towards enantiomers of some amino acid esters and 1-arylethylamins were examined by UV-titration method. These receptor compounds exhibited strong complexation (with Ka up to 5787.23 M-1) and very good enantioselectivity (up to KaS/KaR= 13.98).

Peak-fitting assisted SERS strategy for accurate discrimination of carboxylic acid enantiomers.

A novel peak-fitting assisted SERS (PF-SERS) strategy was developed for the first time to discriminate carboxylic acid enantiomers. The PF-SERS method offered substantial improvement in accuracy, quantitative performance of enantioselective sensing and exceptionally strong enantiomeric recognition ability.

Dehydroabietic acid-based chiral ionic liquids: Their synthesis and potential enantiomeric recognition ability

Abstract Several new chiral imidazolinium ionic liquids (CILs) have been synthesized by using optically pure dehydroabietic acid (DA) as the chiral precursor. Their enantiomeric recognition abilities were measured using rac-mandelic acid n-Bu4N salt as the substrate by NMR spectroscopy. Based on the structure-interaction relationships, the bulky anion and the side chain linking the DA group to the imidazole ring have crucial effects on CIL recognition. The 1H NMR measurements indicated that [MimMeDA]NTf2 exhibits good and versatile molecular recognition ability. The new DA-based CILs reported here may be interesting chiral media for enantioselective reactions and useful in enantiomeric separations.

Harnessing the enantiomeric recognition ability of hydrophobic polymers of intrinsic microporosity (PIM-1) toward amino acids by converting them into hydrophilic polymer dots

In this work, we synthesized novel polymer dots (Pdots) from polymers of intrinsic microporosity (PIM-1) containing a racemic mixture of R- and S-chiral centers as the hydrophobic conjugated polymer chains.

Synthesis and application of novel carbohydrate-based ammonium and triazolium salts

The synthesis of nine new carbohydrate-based quaternary ammonium salts and two new triazolium salts starting from d-glucose has been accomplished. Our synthesis utilized the regio- and stereoselective ring opening reaction of 2,3-anhydro sugars by nucleophilic reagents to afford the key intermediates. In these new types of phase transfer catalysts, the ammonium and triazolium functions are directly attached to the carbohydrate scaffold in different positions (2-, 3-, 6-positions of the sugar). The efficiency of the altrose- and glucose-based quaternary salts were tested in the alkylation of N-(diphenyl) methylene glycine tert-butyl ester with benzyl bromide. To our knowledge this is the first example when sugar-based quaternary ammonium or triazolium salts were used successfully as phase transfer catalysts. The enantiomeric recognition ability of the synthesized salts towards racemic Mosher’s acid silver salt was also investigated by 19F NMR spectroscopy.

Novel chiral Oxa-bridged Calix[2]arene[2]triazine derivatives as NMR chiral reagents for enantioselective recognition of α-racemic carboxylic acids

A new family of chiral tetraoxacalix[2]arene[2]triazine receptors (2a–2c) have been synthesized efficiently in 69–73% yields. By 1H NMR spectroscopy, the chiral enantiodiscrimination ability of novel hosts against a series racemic carboxylic acids were examined. The chiral calix[2]arene[2]triazine-based compounds were found to have good enantiomeric recognition ability to racemic carboxylic acids. We also observed that the tetraoxacalix[2]arene[2]triazine derivative 2c is a more versatile chiral solvating agents than 2a and 2b, as 2c shows a better performance for the determination of the enantiomeric excess. The molar ratio of the each enantiomers of guest molecules with receptors were examined by using Job plots, respectively. The graphics show that the hosts form 1:1 complexes with all of the guests.

Synthesis and characterization of chiral ionic liquids based on quinine, l-proline and l-valine for enantiomeric recognition

The separation of enantiomers remains a major challenge for the pharmaceutical industry. In this work, eight chiral ionic liquids (CILs) directly derived from the ‘chiral pool’ were synthesized and characterized in order to develop enantioselective systems, for the chiral resolution. According to their chiral cations, three different groups of CILs were prepared, namely based on quinine, l-proline and l-valine, and their enantiomeric recognition ability evaluated. For that purpose the diastereomeric interactions between a racemic mixture of Mosher's acid sodium salt and each CIL were studied using 19F NMR spectroscopy. The remarkable chemical shift dispersion induced by some CILs demonstrates their potential application in chiral resolution. Additionally the optical rotation, thermophysical properties and ecotoxicity against the marine bacteria Aliivibrio fischeri of these chiral ionic liquids were addressed.

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 enantiomeric recognition studies of optically active 5,5-dioxophenothiazine bis(urea) and bis(thiourea) derivatives

Novel optically active 5,5-dioxophenothiazine bis(urea) and bis(thiourea) derivatives were synthesized and their enantiomeric recognition abilities toward the enantiomers of tetrabutylammonium salts of α-hydroxy and N-protected α-amino acids were examined in acetonitrile using fluorescence spectroscopy.

Synthesis and Enantiomeric Recognition Studies of Optically Active Pyridino-Crown Ethers Containing an Anthracene Fluorophore Unit.

Novel enantiopure pyridino-18-crown-6 ether-based sensor molecules containing an anthracene fluorophore unit were synthesized. Their enantiomeric recognition abilities toward the enantiomers of 1-phenylethylamine hydrogen perchlorate (PhEt), 1-(1-naphthyl)ethylamine hydrogen perchlorate (NapEt), phenylglycine methyl ester hydrogen perchlorate (PhgOMe), and phenylalanine methyl ester hydrogen perchlorate (PheOMe) were examined in acetonitrile using fluorescence spectroscopy. The sensor molecules showed appreciable enantiomeric recognition toward the enantiomers of NapEt, PhEt, and PhgOMe. The highest enantioselectivity was found in the case of crown ether containing isobutyl groups in the macroring and the enantiomers of NapEt. Chirality 28:562-568, 2016. © 2016 Wiley Periodicals, Inc.

New chiral oxo-bridged calix[2]arene[2]triazine for the enantiomeric recognition of α-racemic carboxylic acids

The enantiomeric excess is a key parameter for chemical and pharmaceutical industries for its ability to determine the activity and therapeutic action of chiral compounds. The determination of the enantiomeric excess using nuclear magnetic resonance is generally based on the formation of diastereomeric complexes. Herein we report novel chiral oxo-bridged calix[2]arene[2]triazine derivatives, which were synthesized from (1S,2R)-(−)-1-amino-2-indanol or (1S,2R)-(+)-2-amino-1,2-diphenylethanol. The structures of these compounds were established by various spectroscopic methods. Their enantiomeric recognition abilities towards the enantiomers of α-racemic carboxylic acids were examined by using 1H NMR spectroscopy. The ΔΔδ values of α-H signals were appropriate to give a good baseline resolution for most of the tested analytes, which ranged from 0.005 to 0.053ppm. The α-hydroxy acids, especially those containing aromatic group such as mandelic acid, α-methoxyphenylacetic acid, showed a bigger ΔΔδ value in comparison to the other carboxylic acids.

Preparation of surface imprinted material of single enantiomer of mandelic acid with a new surface imprinting technique and study on its chiral recognition and resolution properties

A surface imprinted material of the single enantiomer of mandelic acid with high performance was successfully prepared with a new surface imprinting technique of synchronously graft-polymerizing and molecule imprinting, and its enantiomeric recognition and resolution properties were investigated. Micro-sized silica gel particles were first modified with coupling agent γ-mercaptopropyl trimethoxysilane (MPMS), obtaining the modified particles MPMS-SiO2 on which mercapto groups were introduced. A surface initiating system of −SH/BPO was constituted with the mercapto group (-SH) on MPMS-SiO2 particles and dibenzoyl peroxide (BPO) in N,N-dimethyl formamide (DMF) solution. In DMF solution, (R)-mandelic acid molecule was used as the template and the functional monomer hydroxyethyl methylacrylate (HEMA) were combined together by right of multi-site hydrogen bonds. The free radicals produced on MPMS-SiO2 particles initiate HEMA molecules around (R)-mandelic acid molecules and the crosslinking agent N,N'-Methylenebisacrylamide (MBA) to produce graft/crosslinking-polymerization. At the same time, the template (R)-mandelic acid molecules were enveloped within the thin grafted polymer layer on the surfaces of SiO2 particles, obtaining (R)-mandelic acid surface imprinted material MIP-PHEMA/SiO2. The experimental results show that MIP-PHEMA/SiO2 particles have excellent enantiomeric recognition and resolution ability. The binding capacity of MIP-PHEMA/SiO2 particles for (R)-mandelic acid reaches up to 278mg/g. As the resolution experiment of a racemic mixture was carried out with MIP-PHEMA/SiO2 particles as solid adsorbent, relative another enantiomer, (S)-mandelic acid, the selectivity coefficient of the imprinted particles for (R)-mandelic acid is 5.02. As a consequence, the two enantiomers were well separated, and the optical purities (ee values) of the supernatant and eluant get up to 44% (corresponding to (S)-mandelic acid excess) and 85% (corresponding to (R)-mandelic acid excess), respectively.

Synthesis of new chiral calix[4]arene thiourea derivatives for enantiomeric recognition of carboxylate anions

The study of enantiomeric recognition of amino acid and carboxylic acid compounds is of significance since these compounds are basic building blocks of biological molecules. Enantiomeric recognition and separation of these compounds are among the main topics of supramolecular chemistry since they are basic building blocks of biological molecules and a number of them are known to possess potent biological activities. In this study the synthesis of novel chiral calix[4]arene thiourea derivatives has been reported. The enantioselectivity of chiral receptors was investigated by using UV–Vis spectroscopy. All the chiral calix[4]arene derivatives exhibited certain chiral recognition towards the enantiomers of α-hydroxy isovaleric acid (HIVA), mandelic acid (MA), 2-chloromandelic acid (2-ClMA) and N-Boc-alanine (N-BocAl). The receptors with hydrogen bonding sites and aromatic groups showed considerable higher stereoselectivities. As a chiral receptor, calix[4]arene 2-hydroxy-1,2 diphenyl ether thiourea derivative has enantiomeric discriminating ability for 2-chloromandelic acid (up to KR/KS = 2.80) at 25 °C. The enantiomeric recognition abilities for guests are also discussed from a thermodynamic point of view.

Synthesis and enantiomeric recognition studies of optically active acridone bis(urea) and bis(thiourea) derivatives

Novel optically active acridone bis(urea) and bis(thiourea) derivatives were synthesized and their enantiomeric recognition abilities towards the enantiomers of tetrabutylammonium salts of α-hydroxy and N-protected α-amino acids were examined in acetonitrile–DMSO 99:1 using fluorescence spectroscopy.

Synthesis and amines enantiomeric recognition ability of binaphthyl-appended 22-crown-6 ethers derived from rosin acid

Novel chiral 22-crown-6 ethers (5a–b) bearing methoxycarbonyl side groups derived from rosin acid and 2,2′-dihydroxy-1,1′-binaphthyl (BINOL) were prepared in optically pure forms, and their enantiodiscriminating abilities toward protonated primary amines and amino acid methyl ester salts were examined by the UV–vis titration method. These receptors exhibit good chiral recognition towards the isomers (up to KL/KD = 5.23, ΔΔG0 = 4.10 kJ mol−1) in CHCl3:MeOH = 2:1 at 25 °C.

Application of L‐proline derivatives as chiral shift reagents for enantiomeric recognition of carboxylic acids

Four proline-derived chiral receptors 5-8 were readily synthesized starting from L-proline. The enantiomeric recognition ability of chiral receptors was examined with a series of carboxylic acids by (1) H NMR spectroscopy. The molar ratio and the association constants of the chiral compounds with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that the hosts form 1:1 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. Among the chiral receptors used in this study, prolinamide 6 was found to be the best chiral shift reagent and is effective for the determination of the enantiomeric excess of chiral carboxylic acids.

Synthesis and enantiomeric recognition ability of 22-crown-6 ethers derived from rosin acid and BINOL

Four novel chiral 22-crown-6 ethers 6a– b, 7a– b bearing hydroxyl side groups derived from rosin acid and BINOL were prepared in optically pure forms, and their enantiodiscriminating abilities towards protonated primary amines and amino acid methyl ester salts were examined by UV–vis titration methods. These receptors exhibited good chiral recognition towards the isomers (up to K D/ K L = 6.02, ΔΔ G 0 = 4.45 kJ mol −1) and showed different complementarity to various chiral guests.