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Benedetto Natalini - One of the best experts on this subject based on the ideXlab platform.
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last ten years 2008 2018 of chiral Ligand Exchange Chromatography in hplc an updated review
Journal of Separation Science, 2019Co-Authors: Federica Ianni, Lucia Pucciarini, Andrea Carotti, Serena Natalini, G Z Raskildina, Roccaldo Sardella, Benedetto NataliniAbstract:Chiral Ligand-Exchange Chromatography is one of the elective strategies for the direct enantioresolution of small chelating compounds: amino acids, diamines, amino alcohols, diols, small peptides, etc. Unlike other methods, the interaction between chiral selector and analyte enantiomers is mediated by a cation, thus producing diastereomeric ternary complexes. Two main approaches are conventionally applied in chiral Ligand-Exchange Chromatography. The first relies upon chiral stationary phases where the chiral selector is either covalently immobilized or physically adsorbed onto suitable packing materials (coated phases). In the second approach, chiral molecules are added to the eluent, thus generating chiral eluent systems. Among the advantages of chiral Ligand-Exchange Chromatography, the generation of UV/vis-active metal complexes, and the use of commercially available or easy-to-synthesize chiral selectors, in combination to rather inexpensive achiral columns for coated phases and chiral eluents, are noteworthy. Besides amino acids and amino alcohols, other species have proven suitable for chiral Ligand-Exchange Chromatography applications. Recently, the use of either chiral ionic liquids or micellar liquid Chromatography systems as well as the successful off-column formation of diastereomeric complexes have expanded the selectivity profiles and application fields. All of these issues are touched in the review, shedding light to the contributions appeared in the last decade.
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n decyl s trityl r cysteine a new chiral selector for green Ligand Exchange Chromatography applications
Journal of Pharmaceutical and Biomedical Analysis, 2017Co-Authors: Andrea Carotti, Federica Ianni, Lucia Pucciarini, Roccaldo Sardella, Maura Marinozzi, Emidio Camaioni, Benedetto NataliniAbstract:Abstract In search for new enantioselectivity profiles, the N-decyl-S-trityl-(R)-cysteine [C10-(R)-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for Ligand-Exchange Chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0 mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C10-(R)-STC-based CSP, with resolution factor (RS) values up to 8.86. Conformationally rigid and hydrophobic Ligands often experienced the largest enantioselectivity effects. A high loadability emerged from the analysis of rac-NorVal (selected as prototype test compound): up to 20 mg/mL were efficiently enantioseparated with the CLEC-CSP. Two in-line hand-made cartridges filled with a strong cation-Exchange resin allowed the effective catching of Cu(II) ions after the semi-preparative enantioseparation. The quantitative recovery of the rac-NorVal enantiomers was made possible by flowing through the cartridge a 5% (v) ammonia solution. The CLEC phase proved successful in the enantioselective analysis of a commercially available (S)-Leu containing tablet. Furthermore, in order to understand the molecular basis for a successful use of the C10-(R)-STC-based CLEC system, a descriptive structure-separation relationship study was performed. As a result, all compounds with a MEAN-QPlogS (a hydrophilicity descriptor) value lower than 0.373 can be most likely enantioseparated with the CLEC system under investigation. In the work, the numerous aspects complying with the principles of green Chromatography are highlighted and discussed.
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cyclopropyl containing sulfonyl amino acids exploring the enantioseparation through chiral Ligand Exchange Chromatography
Russian Journal of General Chemistry, 2017Co-Authors: Roccaldo Sardella, Federica Ianni, Lucia Pucciarini, Maura Marinozzi, S S Zlotskii, Benedetto NataliniAbstract:In the scope of a broader study focused on glutamate receptors regulators, we have been engaged in synthesis, analysis and pharmacological characterization of rigid analogues of glutamic acid. These compounds exhibited the bioisosteric replacement of the distal carboxylic group with the sulfonic one. Besides the sophisticated synthetic approach, we targeted preparation of a series of cyclopropyl-containing sulfonyl amino acids and development of a chromatographic enantioselective method suitable for distinguishing and quantifying the resulting isomers. Due to chelating ability, the chiral Ligand-Exchange Chromatography (CLEC) was used for diastereo- and enantioseparation of the synthesized compounds. The CLEC-based enantioseparation was achieved by using a chiral mobile phase (CMP) system with N,N-dimethyl-(S)-phenylalanine [(S)-DMP] as the chiral selector. Only one of the investigated enantiomeric pairs was undiscriminated with the employed CLEC–CMP system which, very importantly, produced the simultaneous diastereo- and enantioseparation of two compounds of the series. Furthermore, the large α and RS values computed for three enantiomer pairs could be a good basis for a successful scale-up to a semi-preparative level.
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s trityl r cysteine a multipurpose chiral selector for Ligand Exchange liquid Chromatography applications
Critical Reviews in Analytical Chemistry, 2015Co-Authors: Roccaldo Sardella, Federica Ianni, Maura Marinozzi, Antonella Lisanti, Stefania Scorzoni, Benedetto NataliniAbstract:The stratification of 0.040–0.050 g of S-trityl-(R)-cysteine ((R)-STC) onto a conventional ODS phase produces a very effective (α and RS up to 5.71 and 12.09, respectively) and stable (more than 30 days of repeated analysis) chiral Ligand-Exchange Chromatography (CLEC) coated chiral stationary phase (C-CSP). With a few specific exceptions, a (R) < (S) enantiomer elution order can be easily predicted. The (R)-STC-based C-CSP can be successfully exploited also at a preparative level for enantioisolations of CNS active amino acids (AAs), with a racemate loadability up to 0.015 g for single injection. The CLEC (R)-STC-based system can be helpful in monitoring the presence of (R)-AAs in edible products and other organic materials, thus contributing to evaluating product quality and diagnosing subclinical pathological states in animals and humans. Very profitably, molecular modeling–based computer-assisted classification analyses can reveal the actual enantioseparation ability of the (R)-STC phase towards a spe...
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use of an o benzyl s serine containing eluent for the efficient Ligand Exchange Chromatography based enantioseparation of constrained glutamate receptor Ligands
Analytical Letters, 2015Co-Authors: Federica Ianni, Roccaldo Sardella, Antonella Lisanti, Nicola Giacche, Paola Conti, Andrea Pinto, Lucia Tamborini, Benedetto NataliniAbstract:Four dihydroisoxazole prolines and four dihydroisoxazole cyclopentane derivatives were submitted to chiral Ligand-Exchange chromatographic analysis in the presence of O-benzyl-(S)-serine, as the chiral mobile phase additive to the eluent. The 1.0 mM O-benzyl-(S)-serine and 0.5 mM Cu(NO3)2 eluent flowed at 1.0 mL/min through a conventional octadecylsilica-based stationary phase maintained at 25°C and provided excellent levels of enantioselectivity and resolution for all the species. By using enantiomers as model compounds, the method was validated revealing that the mixed ternary diastereomeric eluates present slightly different spectroscopic properties. The selected chiral Ligand-Exchange Chromatography method was applied for semi-preparative enantioisolation that allowed the establishment of the k(−) < k(+) enantiomeric elution order.
Roccaldo Sardella - One of the best experts on this subject based on the ideXlab platform.
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last ten years 2008 2018 of chiral Ligand Exchange Chromatography in hplc an updated review
Journal of Separation Science, 2019Co-Authors: Federica Ianni, Lucia Pucciarini, Andrea Carotti, Serena Natalini, G Z Raskildina, Roccaldo Sardella, Benedetto NataliniAbstract:Chiral Ligand-Exchange Chromatography is one of the elective strategies for the direct enantioresolution of small chelating compounds: amino acids, diamines, amino alcohols, diols, small peptides, etc. Unlike other methods, the interaction between chiral selector and analyte enantiomers is mediated by a cation, thus producing diastereomeric ternary complexes. Two main approaches are conventionally applied in chiral Ligand-Exchange Chromatography. The first relies upon chiral stationary phases where the chiral selector is either covalently immobilized or physically adsorbed onto suitable packing materials (coated phases). In the second approach, chiral molecules are added to the eluent, thus generating chiral eluent systems. Among the advantages of chiral Ligand-Exchange Chromatography, the generation of UV/vis-active metal complexes, and the use of commercially available or easy-to-synthesize chiral selectors, in combination to rather inexpensive achiral columns for coated phases and chiral eluents, are noteworthy. Besides amino acids and amino alcohols, other species have proven suitable for chiral Ligand-Exchange Chromatography applications. Recently, the use of either chiral ionic liquids or micellar liquid Chromatography systems as well as the successful off-column formation of diastereomeric complexes have expanded the selectivity profiles and application fields. All of these issues are touched in the review, shedding light to the contributions appeared in the last decade.
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n decyl s trityl r cysteine a new chiral selector for green Ligand Exchange Chromatography applications
Journal of Pharmaceutical and Biomedical Analysis, 2017Co-Authors: Andrea Carotti, Federica Ianni, Lucia Pucciarini, Roccaldo Sardella, Maura Marinozzi, Emidio Camaioni, Benedetto NataliniAbstract:Abstract In search for new enantioselectivity profiles, the N-decyl-S-trityl-(R)-cysteine [C10-(R)-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for Ligand-Exchange Chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0 mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C10-(R)-STC-based CSP, with resolution factor (RS) values up to 8.86. Conformationally rigid and hydrophobic Ligands often experienced the largest enantioselectivity effects. A high loadability emerged from the analysis of rac-NorVal (selected as prototype test compound): up to 20 mg/mL were efficiently enantioseparated with the CLEC-CSP. Two in-line hand-made cartridges filled with a strong cation-Exchange resin allowed the effective catching of Cu(II) ions after the semi-preparative enantioseparation. The quantitative recovery of the rac-NorVal enantiomers was made possible by flowing through the cartridge a 5% (v) ammonia solution. The CLEC phase proved successful in the enantioselective analysis of a commercially available (S)-Leu containing tablet. Furthermore, in order to understand the molecular basis for a successful use of the C10-(R)-STC-based CLEC system, a descriptive structure-separation relationship study was performed. As a result, all compounds with a MEAN-QPlogS (a hydrophilicity descriptor) value lower than 0.373 can be most likely enantioseparated with the CLEC system under investigation. In the work, the numerous aspects complying with the principles of green Chromatography are highlighted and discussed.
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cyclopropyl containing sulfonyl amino acids exploring the enantioseparation through chiral Ligand Exchange Chromatography
Russian Journal of General Chemistry, 2017Co-Authors: Roccaldo Sardella, Federica Ianni, Lucia Pucciarini, Maura Marinozzi, S S Zlotskii, Benedetto NataliniAbstract:In the scope of a broader study focused on glutamate receptors regulators, we have been engaged in synthesis, analysis and pharmacological characterization of rigid analogues of glutamic acid. These compounds exhibited the bioisosteric replacement of the distal carboxylic group with the sulfonic one. Besides the sophisticated synthetic approach, we targeted preparation of a series of cyclopropyl-containing sulfonyl amino acids and development of a chromatographic enantioselective method suitable for distinguishing and quantifying the resulting isomers. Due to chelating ability, the chiral Ligand-Exchange Chromatography (CLEC) was used for diastereo- and enantioseparation of the synthesized compounds. The CLEC-based enantioseparation was achieved by using a chiral mobile phase (CMP) system with N,N-dimethyl-(S)-phenylalanine [(S)-DMP] as the chiral selector. Only one of the investigated enantiomeric pairs was undiscriminated with the employed CLEC–CMP system which, very importantly, produced the simultaneous diastereo- and enantioseparation of two compounds of the series. Furthermore, the large α and RS values computed for three enantiomer pairs could be a good basis for a successful scale-up to a semi-preparative level.
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s trityl r cysteine a multipurpose chiral selector for Ligand Exchange liquid Chromatography applications
Critical Reviews in Analytical Chemistry, 2015Co-Authors: Roccaldo Sardella, Federica Ianni, Maura Marinozzi, Antonella Lisanti, Stefania Scorzoni, Benedetto NataliniAbstract:The stratification of 0.040–0.050 g of S-trityl-(R)-cysteine ((R)-STC) onto a conventional ODS phase produces a very effective (α and RS up to 5.71 and 12.09, respectively) and stable (more than 30 days of repeated analysis) chiral Ligand-Exchange Chromatography (CLEC) coated chiral stationary phase (C-CSP). With a few specific exceptions, a (R) < (S) enantiomer elution order can be easily predicted. The (R)-STC-based C-CSP can be successfully exploited also at a preparative level for enantioisolations of CNS active amino acids (AAs), with a racemate loadability up to 0.015 g for single injection. The CLEC (R)-STC-based system can be helpful in monitoring the presence of (R)-AAs in edible products and other organic materials, thus contributing to evaluating product quality and diagnosing subclinical pathological states in animals and humans. Very profitably, molecular modeling–based computer-assisted classification analyses can reveal the actual enantioseparation ability of the (R)-STC phase towards a spe...
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use of an o benzyl s serine containing eluent for the efficient Ligand Exchange Chromatography based enantioseparation of constrained glutamate receptor Ligands
Analytical Letters, 2015Co-Authors: Federica Ianni, Roccaldo Sardella, Antonella Lisanti, Nicola Giacche, Paola Conti, Andrea Pinto, Lucia Tamborini, Benedetto NataliniAbstract:Four dihydroisoxazole prolines and four dihydroisoxazole cyclopentane derivatives were submitted to chiral Ligand-Exchange chromatographic analysis in the presence of O-benzyl-(S)-serine, as the chiral mobile phase additive to the eluent. The 1.0 mM O-benzyl-(S)-serine and 0.5 mM Cu(NO3)2 eluent flowed at 1.0 mL/min through a conventional octadecylsilica-based stationary phase maintained at 25°C and provided excellent levels of enantioselectivity and resolution for all the species. By using enantiomers as model compounds, the method was validated revealing that the mixed ternary diastereomeric eluates present slightly different spectroscopic properties. The selected chiral Ligand-Exchange Chromatography method was applied for semi-preparative enantioisolation that allowed the establishment of the k(−) < k(+) enantiomeric elution order.
Roberto Pellicciari - One of the best experts on this subject based on the ideXlab platform.
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computational studies for the elucidation of the enantiomer elution order of amino acids in chiral Ligand Exchange Chromatography
Journal of Chromatography A, 2010Co-Authors: Benedetto Natalini, Federica Ianni, Roccaldo Sardella, Nicola Giacche, Antonio Macchiarulo, Roberto PellicciariAbstract:Owing to the exceptional sophistication of chiral Ligand-Exchange Chromatography (CLEC) systems operating in the presence of chiral mobile phase (CMP) additives, only few studies dealing with mechanistic investigations have been presented so far. Nevertheless, dedicated computational protocols applied to simplified models, can furnish valuable information on the factors that mainly affect the overall enantiorecognition event. Accordingly, the extraordinary accordance observed between quantum mechanical (QM) calculations and crystallographic data led us to use optimized ternary complexes carrying the chiral selector O-benzyl-(S)-serine [(S)-OBS], as starting structures to build up a computational model enabling to explain the enantiomer elution order of amino acids with this enantioresolving agent. As a result of the calculation of 113 three-dimensional descriptors on the mixed complexes, and the generation of a decision tree, the delta-Energy of solvation (delta-E(sol)) was found to correctly classify all the compounds of the training set (20 species) according to the relative chromatographic behaviour. Thus, as a rule of thumb, the diastereomeric couples having a delta-E(sol) value lower than 5.321 kcal/mol (splitting node) experienced a "canonical" enantiomer elution order while an opposite situation occurred for all the others (reversed elution profile). The profitable predictive power of the developed model was assessed on the selected test set (5 species).
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the effect of the copper ii salt anion in the chiral Ligand Exchange Chromatography of amino acids
Analytica Chimica Acta, 2009Co-Authors: Benedetto Natalini, Roccaldo Sardella, Giovanni Carbone, Antonio Macchiarulo, Roberto PellicciariAbstract:Abstract Due to the strong involvement in numerous biochemical processes, the separation and resolution of amino acids is a continuously challenging task. Among the experimental parameters affecting the performances in a Chiral Ligand-Exchange Chromatography (CLEC) environment, the effect of the copper(II) salt counter-ion has received very limited attention. Aimed at evaluating the Cu(II) counter-ion effect upon the overall chromatographic performances when the S-trityl-(R)-cysteine is adopted as the chiral selector for the coated stationary phase, a number of both organic (acetate, formate, trifluoromethane-sulfonate) and inorganic (bromide, chloride, nitrate, perchlorate, sulfate) salts has been engaged for the enantiomer separation of a selected set of aliphatic (Allo-Ile, Ile, Leu, Nor-Leu, Nor-Val, Val) and aromatic (AIDA, ATIDA, His, Phe, Phg, Tyr) amino acids. By varying the physico-chemical nature of the Cu(II) anion, a pronounced impact upon the resolution factor (RS) has been observed. Even if to a lesser extent, the enantioseparation factor values (α) underwent variation, as well. A molecular modelling investigation has also been carried out as a rationalization attempt of the observed chromatographic outcomes.
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descriptive structure separation relationship studies in chiral Ligand Exchange Chromatography
Journal of Separation Science, 2008Co-Authors: Benedetto Natalini, Roccaldo Sardella, Antonio Macchiarulo, Alberto Massarotti, Roberto PellicciariAbstract:A new approach to model and interpret the separation of amino acid enantiomers is described. The descriptive structure-separation relationship (DSSR) study of a set of amino acid enantiomer couples analyzed with two chiral selectors S-benzyl-(R)-cysteine ((R)-SBC) and S-trityl-(R)-cysteine ((R)-STC) has been performed with the aim to highlight the molecular properties of the analyte affecting the enantiodiscrimination process. Although with some exceptions, the classification models obtained with (R)-STC indicate that the partial positive surface area (PPSA-1) is the suitable descriptor to account for the separation of both (R)- and (S)-enantiomers. On the other hand, two different descriptors characterize the separation process with (R)-SBC. While fractional negatively charged partial surface area (FNSA-3) results the discriminating descriptor for (R)-enantiomers, the relative polar surface area (RPSA) is able to best discriminate among (S)-enantiomers.
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s trityl r cysteine a powerful chiral selector for the analytical and preparative Ligand Exchange Chromatography of amino acids
Journal of Separation Science, 2008Co-Authors: Benedetto Natalini, Roccaldo Sardella, Antonio Macchiarulo, Roberto PellicciariAbstract:S-Trityl-(R)-cysteine [(R)-STC] is the new selector of a dynamically coated, chiral Ligand-Exchange stationary phase which proved to be highly effective in both analytical and preparative-scale separation of enantiomers of some natural and unnatural underivatized amino acids, with good separation and resolution factors. With the aim of identifying the best chromatographic conditions suitable for the preparative-scale separations, some parameters controlling retention, separation and resolution factors (such as the type and amount of cupric salt and the eluent pH) were investigated. The relatively easy removal of the Cu(II) ions renders this technique suitable for obtaining small amounts of enantiomerically pure samples for preliminary biological evaluations.
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s α α di 2 naphthyl 2 pyrrolidinemethanol a useful tool to study the recognition mechanism in chiral Ligand Exchange Chromatography
Journal of Separation Science, 2007Co-Authors: Benedetto Natalini, Serena Natalini, Roccaldo Sardella, Antonio Macchiarulo, Roberto PellicciariAbstract:A dynamic coating of the RP-18 carbon chain layers with the new chiral selector (S)-(-)-alpha,alpha-di(2-naphthyl)-2-pyrrolidinemethanol allowed the formation of a mixed chiral stationary phase that has been used in the separation of a selected set of amino acid racemates. Both a representative model and classification structure-property relationship studies have been performed in order to study the contribution of hydrophobic, bulky and electron-donating groups in the side chain of the chiral selector to the mechanism of chiral recognition.
Federica Ianni - One of the best experts on this subject based on the ideXlab platform.
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last ten years 2008 2018 of chiral Ligand Exchange Chromatography in hplc an updated review
Journal of Separation Science, 2019Co-Authors: Federica Ianni, Lucia Pucciarini, Andrea Carotti, Serena Natalini, G Z Raskildina, Roccaldo Sardella, Benedetto NataliniAbstract:Chiral Ligand-Exchange Chromatography is one of the elective strategies for the direct enantioresolution of small chelating compounds: amino acids, diamines, amino alcohols, diols, small peptides, etc. Unlike other methods, the interaction between chiral selector and analyte enantiomers is mediated by a cation, thus producing diastereomeric ternary complexes. Two main approaches are conventionally applied in chiral Ligand-Exchange Chromatography. The first relies upon chiral stationary phases where the chiral selector is either covalently immobilized or physically adsorbed onto suitable packing materials (coated phases). In the second approach, chiral molecules are added to the eluent, thus generating chiral eluent systems. Among the advantages of chiral Ligand-Exchange Chromatography, the generation of UV/vis-active metal complexes, and the use of commercially available or easy-to-synthesize chiral selectors, in combination to rather inexpensive achiral columns for coated phases and chiral eluents, are noteworthy. Besides amino acids and amino alcohols, other species have proven suitable for chiral Ligand-Exchange Chromatography applications. Recently, the use of either chiral ionic liquids or micellar liquid Chromatography systems as well as the successful off-column formation of diastereomeric complexes have expanded the selectivity profiles and application fields. All of these issues are touched in the review, shedding light to the contributions appeared in the last decade.
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n decyl s trityl r cysteine a new chiral selector for green Ligand Exchange Chromatography applications
Journal of Pharmaceutical and Biomedical Analysis, 2017Co-Authors: Andrea Carotti, Federica Ianni, Lucia Pucciarini, Roccaldo Sardella, Maura Marinozzi, Emidio Camaioni, Benedetto NataliniAbstract:Abstract In search for new enantioselectivity profiles, the N-decyl-S-trityl-(R)-cysteine [C10-(R)-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for Ligand-Exchange Chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0 mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C10-(R)-STC-based CSP, with resolution factor (RS) values up to 8.86. Conformationally rigid and hydrophobic Ligands often experienced the largest enantioselectivity effects. A high loadability emerged from the analysis of rac-NorVal (selected as prototype test compound): up to 20 mg/mL were efficiently enantioseparated with the CLEC-CSP. Two in-line hand-made cartridges filled with a strong cation-Exchange resin allowed the effective catching of Cu(II) ions after the semi-preparative enantioseparation. The quantitative recovery of the rac-NorVal enantiomers was made possible by flowing through the cartridge a 5% (v) ammonia solution. The CLEC phase proved successful in the enantioselective analysis of a commercially available (S)-Leu containing tablet. Furthermore, in order to understand the molecular basis for a successful use of the C10-(R)-STC-based CLEC system, a descriptive structure-separation relationship study was performed. As a result, all compounds with a MEAN-QPlogS (a hydrophilicity descriptor) value lower than 0.373 can be most likely enantioseparated with the CLEC system under investigation. In the work, the numerous aspects complying with the principles of green Chromatography are highlighted and discussed.
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cyclopropyl containing sulfonyl amino acids exploring the enantioseparation through chiral Ligand Exchange Chromatography
Russian Journal of General Chemistry, 2017Co-Authors: Roccaldo Sardella, Federica Ianni, Lucia Pucciarini, Maura Marinozzi, S S Zlotskii, Benedetto NataliniAbstract:In the scope of a broader study focused on glutamate receptors regulators, we have been engaged in synthesis, analysis and pharmacological characterization of rigid analogues of glutamic acid. These compounds exhibited the bioisosteric replacement of the distal carboxylic group with the sulfonic one. Besides the sophisticated synthetic approach, we targeted preparation of a series of cyclopropyl-containing sulfonyl amino acids and development of a chromatographic enantioselective method suitable for distinguishing and quantifying the resulting isomers. Due to chelating ability, the chiral Ligand-Exchange Chromatography (CLEC) was used for diastereo- and enantioseparation of the synthesized compounds. The CLEC-based enantioseparation was achieved by using a chiral mobile phase (CMP) system with N,N-dimethyl-(S)-phenylalanine [(S)-DMP] as the chiral selector. Only one of the investigated enantiomeric pairs was undiscriminated with the employed CLEC–CMP system which, very importantly, produced the simultaneous diastereo- and enantioseparation of two compounds of the series. Furthermore, the large α and RS values computed for three enantiomer pairs could be a good basis for a successful scale-up to a semi-preparative level.
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s trityl r cysteine a multipurpose chiral selector for Ligand Exchange liquid Chromatography applications
Critical Reviews in Analytical Chemistry, 2015Co-Authors: Roccaldo Sardella, Federica Ianni, Maura Marinozzi, Antonella Lisanti, Stefania Scorzoni, Benedetto NataliniAbstract:The stratification of 0.040–0.050 g of S-trityl-(R)-cysteine ((R)-STC) onto a conventional ODS phase produces a very effective (α and RS up to 5.71 and 12.09, respectively) and stable (more than 30 days of repeated analysis) chiral Ligand-Exchange Chromatography (CLEC) coated chiral stationary phase (C-CSP). With a few specific exceptions, a (R) < (S) enantiomer elution order can be easily predicted. The (R)-STC-based C-CSP can be successfully exploited also at a preparative level for enantioisolations of CNS active amino acids (AAs), with a racemate loadability up to 0.015 g for single injection. The CLEC (R)-STC-based system can be helpful in monitoring the presence of (R)-AAs in edible products and other organic materials, thus contributing to evaluating product quality and diagnosing subclinical pathological states in animals and humans. Very profitably, molecular modeling–based computer-assisted classification analyses can reveal the actual enantioseparation ability of the (R)-STC phase towards a spe...
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use of an o benzyl s serine containing eluent for the efficient Ligand Exchange Chromatography based enantioseparation of constrained glutamate receptor Ligands
Analytical Letters, 2015Co-Authors: Federica Ianni, Roccaldo Sardella, Antonella Lisanti, Nicola Giacche, Paola Conti, Andrea Pinto, Lucia Tamborini, Benedetto NataliniAbstract:Four dihydroisoxazole prolines and four dihydroisoxazole cyclopentane derivatives were submitted to chiral Ligand-Exchange chromatographic analysis in the presence of O-benzyl-(S)-serine, as the chiral mobile phase additive to the eluent. The 1.0 mM O-benzyl-(S)-serine and 0.5 mM Cu(NO3)2 eluent flowed at 1.0 mL/min through a conventional octadecylsilica-based stationary phase maintained at 25°C and provided excellent levels of enantioselectivity and resolution for all the species. By using enantiomers as model compounds, the method was validated revealing that the mixed ternary diastereomeric eluates present slightly different spectroscopic properties. The selected chiral Ligand-Exchange Chromatography method was applied for semi-preparative enantioisolation that allowed the establishment of the k(−) < k(+) enantiomeric elution order.
Kyung Ho Row - One of the best experts on this subject based on the ideXlab platform.
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investigation of ofloxacin enantioseparation by Ligand Exchange Chromatography
Journal of Chemical Technology & Biotechnology, 2009Co-Authors: Minglei Tian, Hongyuan Yan, Kyung Ho RowAbstract:BACKGROUND: There is much interest in the recognition and determination the two ofloxacin enantiomers, not only from the point of view of investigating the pharmacokinetics of the enantiomers in vitro but also in the design and development of new chiral pharmaceutics. RESULTS: Chiral separation was performed on a C18 column, in which the mobile phase consisted of a methanol–water solution (containing different concentrations of L-phenylalanine and copper sulfate) and its flow rate was set at 0.7 mL min−1. The effect of different kinds and concentration of Ligands, bivalent copper ion, organic modifier, ionic liquid modifier, pH of mobile phase, and temperature on enantioseparation were evaluated and the results show that the enantioselectivity was strongly affected by the pH and Ligand concentration of the mobile phase. Under optimal conditions, baseline separation of the two enantiomers was obtained with a resolution of 4.69 in less than 40 min. CONCLUSION: The mechanism of chiral discrimination is based on the stabilities of the copper(II) binary complexes and their ternary diastereomeric complexes with amino acids formed in solution and stationary phase. The proposed method could be used for the quality evaluation of ofloxacin enantiomers. Copyright © 2009 Society of Chemical Industry
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direct determination of ofloxacin enantiomers in human urine by Ligand Exchange Chromatography
Journal of Liquid Chromatography & Related Technologies, 2007Co-Authors: Hongyuan Yan, Kyung Ho RowAbstract:Abstract A sensitive and simple method for the determination of ofloxacin enantiomers in human urine was developed by Ligand Exchange high performance liquid Chromatography. Chiral separation was performed on a C18 column, where the mobile phase consisted of a methanol‐water solution (containing1.2 mmol L−1 L‐phenylalanine and 1.0 mmol L−1 copper sulphate) (15∶85, v/v) and its flow rate was set at 1.0 mL min−1. After centrifugation, the human urine was injected into a C18 column directly. Baseline separation of ofloxacin enantiomers in human urine were obtained with a resolution of 3.24 in less than 25 min, and no interference by the protein or endogenous compounds were observed. The effects of different separation conditions were investigated and the concentration of Ligand and pH of the mobile phase play a critical role in the enantioseparation. The standard curves showed excellent linearity over the concentration range from 0.8 to 400 µg mL−1 for ofloxacin enantiomers. The linear correlation equations ...
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rapid chiral separation and impurity determination of levofloxacin by Ligand Exchange Chromatography
Analytica Chimica Acta, 2007Co-Authors: Hongyuan Yan, Kyung Ho RowAbstract:A sensitive, simple, and accurate method for determination of levofloxacin and its (R)-enantiomer was developed to determine the chiral impurity of levofloxacin in Cravit Tablets material by Ligand-Exchange high performance liquid Chromatography. The effects of different kinds of Ligands, concentration of Ligands in mobile phase, organic modifier, pH of mobile phase, and temperature on enantioseparation were investigated and evaluated. Chiral separation was performed on a conventional C(18) column, where the mobile phase consisted of a methanol-water solution (containing 10 mmol L(-1)l-leucine and 5 mmol L(-1) copper sulfate) (88:12, v/v) and its flow-rate was set at 1.0 mL min(-1). The conventional C(18) column offers baseline separation of two enantiomers with a resolution of 2.4 in less than 20 min. Thermodynamic data (DeltaDeltaH and DeltaDeltaS) obtained by Van't Hoff plots revealed the chiral separation is an enthalpy-controlled process. The standard curves showed excellent linearity over the concentration range from 0.5 to 400 mg L(-1) for levofloxacin and its (R)-enantiomer. The linear correlation equations are: y=1.33 x 10(5)x+6297 (r=0.9991) and y=1.34 x 10(5)x+3565 (r=0.9997), respectively. The relative standard deviation (RSD) of the method was below 2.3% (n=3).