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A series of highly emissive inert and chiral CrIII complexes displaying positive and negative circularly polarized luminescence (CPL) within the near-infrared (NIR) region at room temperature have been prepared and characterized to decipher the effect of ligand substitution on the photophysical properties, more specifically on the chiroptical properties. The helical homoleptic [Cr(dqp-R)2]3+ (dqp = 2,6-di(quinolin-8-yl)pyridine; R = Ph, ≡-Ph, DMA, ≡-DMA (DMA = N,N-dimethylaniline)) and heteroleptic [Cr(dqp)(L)]3+ (L = 4-methoxy-2,6-di(quinolin-8-yl)pyridine (dqp-OMe) or L = N2,N6-dimethyl-N2,N6-di(pyridin-2-yl)pyridine-2,6-diamine (ddpd)) molecular rubies were synthesized as racemic mixtures and then resolved and isolated into their respective pure PP and MM enantiomeric forms by chiral stationary phase HPLC. The corresponding enantiomers show two opposite polarized emission bands within the 700-780 nm range corresponding to the characteristic metal-centered Cr(2E'→4A2) and Cr(2T1'→4A2) transitions with large glum ranging from 0.14 to 0.20 for the former transition. In summary, this study reports the rational use of different ligands on CrIII and their effect on the chiroptical properties of the complexes. [ABSTRACT FROM AUTHOR]

The hydrolase-catalyzed kinetic resolution of fluorinated racemates of 3-arylcarboxylic acids is described. Hydrolysis of ethyl esters of fluorinated acids by esterases and hydrolases in all cases resulted in the formation of hydrolyzed (S)-carboxylic acids and unreacted (R)-esters in high yields and high enantiomeric purity. The influence of separation conditions on the efficiency and enantioselectivity of biocatalytic conversion was also studied. The reactions were carried out under normal conditions (stirring with a magnetic stirrer at room temperature) and microwave irradiation in the presence of hydrolases. Amano PS showed excellent selectivity and good yields in the hydrolysis of fluorinated aromatic compounds. The absolute configuration of the resulting compounds was based on biokinetic studies and the use of chiral HPLC. A molecular modeling of the kinetic resolution of carboxylic acid esters was carried out. [ABSTRACT FROM AUTHOR]

A series of highly emissive inert and chiral CrIII complexes displaying positive and negative circularly polarized luminescence (CPL) within the near-infrared (NIR) region at room temperature have been prepared and characterized to decipher the effect of ligand substitution on the photophysical properties, more specifically on the chiroptical properties. The helical homoleptic [Cr(dqp-R)2]3+ (dqp = 2,6-di(quinolin-8-yl)pyridine; R = Ph, ≡-Ph, DMA, ≡-DMA (DMA = N,N-dimethylaniline)) and heteroleptic [Cr(dqp)(L)]3+ (L = 4-methoxy-2,6-di(quinolin-8-yl)pyridine (dqp-OMe) or L = N2,N6-dimethyl-N2,N6-di(pyridin-2-yl)pyridine-2,6-diamine (ddpd)) molecular rubies were synthesized as racemic mixtures and then resolved and isolated into their respective pure PP and MM enantiomeric forms by chiral stationary phase HPLC. The corresponding enantiomers show two opposite polarized emission bands within the 700–780 nm range corresponding to the characteristic metal-centered Cr(2E’→4A2) and Cr(2T1’→4A2) transitions with large glum ranging from 0.14 to 0.20 for the former transition. In summary, this study reports the rational use of different ligands on CrIII and their effect on the chiroptical properties of the complexes.

4-Nitro and 7-nitro propranolol have been recently synthesized and characterized by us. (±)-4-NO2-propranolol has been shown to act as a selective antagonist of 6-nitrodopamine (6-ND) receptors in the right atrium of rats. As part of our follow-up to this study, herein, we describe the first synthesis of (±)-3-nitroatenolol as a probe to evaluate the potential nitration of atenolol by endothelium. Chiral chromatography was used to produce pure enantiomers. By using Riguera's method, which is based on the sign distribution of ΔδH, the absolute configuration of the secondary alcohol was determined. [ABSTRACT FROM AUTHOR]

The hydrolase-catalyzed kinetic resolution of fluorinated racemates of 3-arylcarboxylic acids is described. Hydrolysis of ethyl esters of fluorinated acids by esterases and hydrolases in all cases resulted in the formation of hydrolyzed (S)-carboxylic acids and unreacted (R)-esters in high yields and high enantiomeric purity. The influence of separation conditions on the efficiency and enantioselectivity of biocatalytic conversion was also studied. The reactions were carried out under normal conditions (stirring with a magnetic stirrer at room temperature) and microwave irradiation in the presence of hydrolases. Amano PS showed excellent selectivity and good yields in the hydrolysis of fluorinated aromatic compounds. The absolute configuration of the resulting compounds was based on biokinetic studies and the use of chiral HPLC. A molecular modeling of the kinetic resolution of carboxylic acid esters was carried out.

A short and efficient stereo-specific synthesis of three stereoisomers (two diastereomer and one enantiomer) of Oxalate salt of benzyl (2S,5R)-5-(benzyloxyamino)piperidine-2-carboxylate (8) has been described. Compound 8 is a key intermediate in the synthesis of β-lactamase inhibitors, was synthesized in high diastereomeric excess using chirally pure L-pyroglutamic acid. In this report, we also describe a chiral high performance liquid chromatography (CHPLC) method to separate these isomers. The developed CHPLC method was validated for the accurate determination of the diastereomeric purity of compound 8. [ABSTRACT FROM AUTHOR]

Individual (S)-enantiomers of 6-methoxy-, 6-chloro-, and 6-nitro-3-methyl-3,4-di-hydro-2H-[1,4]benzoxazines were synthesized via an acylative kinetic resolution of race-mates using (S)-naproxen acyl chloride as a diastereoselective chiral resolving agent. The acylation of racemic benzoxazines with (S)-naproxen acyl chloride afforded (S,S)-dia-stereomers of amides as the major products, which were isolated in diastereomerically pure form (>99% de) by the recrystallization or flash column chromatography on silica gel. The acidic hydrolysis of (S,S)-amides gave (S)-enantiomers (>99% ee according to chiral HPLC) of 6-substituted 3-methyl-3,4-dihydro-2H-[1,4]benzoxazines. The (R)-enantiomer of 3-methyl-6-nitro-3,4-dihydro-2H-[1,4]benzoxazine (>99% ee) was prepared by the stoichiometric acylation of a scalemic sample with (S)-naproxen acyl chloride followed by the recrystallization of the (R,S)-amide and subsequent acidic hydrolysis. The configuration assignment of the chiral centers in the synthesized benzoxazines was made based on the X-ray diffraction analysis of the corresponding amides. The synthesized enantio-merically pure 6-substituted 3-methylbenzoxazines can be used in the synthesis of biologically active compounds. [ABSTRACT FROM AUTHOR]

Propylene oxide (PO) is an important chemical commodity and a chiral building block to prepare pharmaceutical compounds. It is crucial to develop a sensitive and robust chiral method that can be used to assess the enantiomeric purity of PO and safeguard the quality and safety of pharmaceutical products in commercial quality control (QC) laboratories. A chiral gas chromatography (GC) method based on direct enantioseparation of PO enantiomers on a 50-meter Chiraldex™ A-TA open capillary column was successfully developed for determination of enantiomeric impurity (S)-PO in (R)-PO. However, it was revealed that the chiral GC method lacked adequate robustness for routine use. Consequently, a chiral high-performance liquid chromatography (HPLC) method was developed through pre-column derivatization of PO with 2-naphthalenethiol followed by enantioseparation on a Lux Cellulose-1 (250 mm × 4.6 mm, 5 µm) column. The chiral HPLC method has been demonstrated excellent specificity, sensitivity, accuracy and robustness through method validation and robustness evaluation, thus establishing its suitability for routine use in QC laboratories.

Soai's asymmetric autocatalysis represents a highly remarkable example for spontaneous symmetry breaking and enantioselective amplification in the enantioselective alkylation of pyrimidine‐5‐carbaldehydes to the corresponding chiral pyrimidine alcohols. Recently, zinc hemiacetalate complexes, formed from pyrimidine‐5‐carbaldehydes and the chiral product alcohol, were identified by in situ high‐resolution mass spectrometric measurements as highly active transient asymmetric catalysts in this autocatalytic transformation. To study the formation of such hemiacetals and their stereodynamic properties, we focused on the synthesis of coumarin homolog biaryl systems with carbaldehyde and alcohol substituents. Such systems are able to form hemiacetals by intramolecular cyclization. An interesting feature of the substituted biaryl backbone is that tropos and atropos systems can be obtained, enabling or disabling the intramolecular cyclization to hemiacetals. Biaryl structures with various functional groups were synthesized, and the equilibrium and stereodynamics between the closed and open structures were investigated by dynamic enantioselective HPLC (DHPLC). The enantiomerization barriers ΔGǂ and activation parameters ΔHǂ and ΔSǂ were determined from temperature dependent kinetic measurements. [ABSTRACT FROM AUTHOR]

4-Nitro and 7-nitro propranolol have been recently synthesized and characterized by us. (±)-4-NO2-propranolol has been shown to act as a selective antagonist of 6-nitrodopamine (6-ND) receptors in the right atrium of rats. As part of our follow-up to this study, herein, we describe the first synthesis of (±)-3-nitroatenolol as a probe to evaluate the potential nitration of atenolol by endothelium. Chiral chromatography was used to produce pure enantiomers. By using Riguera’s method, which is based on the sign distribution of ΔδH, the absolute configuration of the secondary alcohol was determined.

Cocoa and chocolate antioxidants might contribute to human health through, for instance, blood flow improvement or blood pressure and glycemia reduction, as well as cognitive function improvement. Unfortunately, polyphenol content is reduced during cocoa fermentation, drying, roasting and all the other phases involved in the chocolate production. Here, we investigated the evolution of the polyphenol content during all the different steps of chocolate production, with a special emphasis on roasting (3 different roasting cycles with 80, 100, and 130 °C as maximum temperature). Samples were followed throughout all processes by evaluating the total polyphenols content, the antioxidant power, the epicatechin content, and epicatechin mean degree of polymerization (phloroglucinol adducts method). Results showed a similar trend for total polyphenol content and antioxidant power with an unexpected bell-shaped curve: an increase followed by a decrease for the three different roasting temperatures. At the intermediate temperature (100 °C), the higher polyphenol content was found just after roasting. The epicatechin content had a trend similar to that of total polyphenol content but, interestingly, the mean degree of polymerization data had the opposite behavior with some deviation in the case of the highest temperature, probably due to epicatechin degradation. It seems likely that roasting can free epicatechin from oligomers, as a consequence of oligomers remodeling. [ABSTRACT FROM AUTHOR]

We recently identified 6-nitrodopamine and other nitro-catecholamines (6-nitrodopa, 6-nitroadrenaline), indicating that the endothelium has the ability to nitrate the classical catecholamines (dopamine, noradrenaline, and adrenaline). In order to investigate whether drugs could be subject to the same nitration process, we synthesized 4-nitro- and 7-nitropropranolol as probes to evaluate the possible nitration of the propranolol by the endothelium. The separation of the enantiomers in very high yields and excellent enantiopurity was achieved by chiral HPLC. Finally, we used Riguera's method to determine the absolute configuration of the enantiomers, through double derivatization with MPA and NMR studies. [ABSTRACT FROM AUTHOR]

A method of analysis was developed for the simultaneous chemo- and enantioseparation of 2-, 3-, and 4-chloromethcathinones by high-performance liquid chromatography tandem mass-spectrometry. The fast method enables the reliable identification of positional isomers of chloromethcathinones in biological samples. In addition, the same method can be used for the enantioselective quantitative determination of one of these compounds and its major phase-1 metabolites in biological fluids. The developed method was applied to oral fluid samples collected by police during routine random traffic control in Belgium from January to November, 2023. It was found that 3-CMC was more frequently abused compared to 4-CMC. Although some differences were observed between the concentrations of enantiomers in OF, most likely the drugs were abused in the racemic form. No abuse of 2-CMC was detected at the timepoint of sample collection. • Simultaneous separation of CMC positional isomers and their enantiomers. • Method applied to human oral fluid samples. • Identification of major phase-1 metabolites of CMCs. [ABSTRACT FROM AUTHOR]

In this study we report on efforts to develop an enantioselective method for the detection of the drug of abuse clephedrone (1-(4-chlorophenyl)-2-(methylamino)-1-propanone (4-chloromethcathinone, also known as 4-CMC or para -chloro-methcathinone)) and its phase-1 metabolites in human biological fluids. The major goal is not to only report results, but primarily to emphasize the various challenges encountered when developing a reliable analytical method for the detection and quantification of novel psychoactive substances (NPS) and their metabolites in the matrix of interest. Such challenges start with the lack of chemical stability of some NPS in biological matrices. Additionally, most often metabolites are unavailable in pure form to serve as analytical standards, just as deuterated standards for native drugs and metabolites are frequently not commercially available. Furthermore, if the NPS is chiral, enantiomerically pure standards with known absolute stereochemistry are required, as well as a stereochemical stability of a drug and its metabolites becomes an issue. In addition, the chirality of a NPS significantly increases the number of species to be detected in the sample and thus challenges the development of an adequate separation method. These issues are shortly addressed, and some solutions offered in this manuscript. • An enantioselective method for quantitative determination of clephedrone and some of its metabolites. • The method was applied to human oral fluid, sweat and urine. • The stability study of clephedrone in human blood, oral fluid and urine was performed. [ABSTRACT FROM AUTHOR]

Stereoselectivity is well known and very pronounced in drug metabolism and receptor binding. However, much less is known about stereoselectivity in drug membrane transport. Here, we characterized the stereoselective cell uptake of chiral phenylethylamine derivatives by human monoamine transporters (NET, DAT, and SERT) and organic cation transporters (OCT1, OCT2, and OCT3). Stereoselectivity differed extensively between closely related transporters. High-affinity monoamine transporters (MATs) showed up to 2.4-fold stereoselective uptake of norepinephrine and epinephrine as well as of numerous analogs. While NET and DAT preferentially transported (S)-norepinephrine, SERT preferred the (R)-enantiomer. In contrast, NET and DAT showed higher transport for (R)-epinephrine and SERT for (S)-epinephrine. Generally, MAT stereoselectivity was lower than expected from their high affinity to several catecholamines and from the high stereoselectivity of some inhibitors used as antidepressants. Additionally, the OCTs differed strongly in their stereoselectivity. While OCT1 showed almost no stereoselective uptake, OCT2 was characterized by a roughly 2-fold preference for most (R)-enantiomers of the phenylethylamines. In contrast, OCT3 transported norphenylephrine and phenylephrine with 3.9-fold and 3.3-fold preference for their (R)-enantiomers, respectively, while the para-hydroxylated octopamine and synephrine showed no stereoselective OCT3 transport. Altogether, our data demonstrate that stereoselectivity is highly transporter-to-substrate specific and highly diverse even between homologous transporters. [ABSTRACT FROM AUTHOR]

A series of highly emissive inert and chiral Cr III complexes displaying positive and negative circularly polarized luminescence (CPL) within the near-infrared (NIR) region at room temperature have been prepared and characterized to decipher the effect of ligand substitution on the photophysical properties, more specifically on the chiroptical properties. The helical homoleptic [Cr(dqp-R) 2 ] 3+ (dqp = 2,6-di(quinolin-8-yl)pyridine; R = Ph, ≡-Ph, DMA, ≡-DMA (DMA = N,N -dimethylaniline)) and heteroleptic [Cr(dqp)(L)] 3+ (L = 4-methoxy-2,6-di(quinolin-8-yl)pyridine (dqp-OMe) or L = N 2 , N 6 -dimethyl- N 2 , N 6 -di(pyridin-2-yl)pyridine-2,6-diamine (ddpd)) molecular rubies were synthesized as racemic mixtures and then resolved and isolated into their respective pure PP and MM enantiomeric forms by chiral stationary phase HPLC. The corresponding enantiomers show two opposite polarized emission bands within the 700-780 nm range corresponding to the characteristic metal-centered Cr( 2 E'→ 4 A 2 ) and Cr( 2 T 1 ' → 4 A 2 ) transitions with large g lum ranging from 0.14 to 0.20 for the former transition. In summary, this study reports the rational use of different ligands on Cr III and their effect on the chiroptical properties of the complexes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Poncet, Besnard, Guénée, Jiménez and Piguet.)

1,4‐Benzoxathiane, 2‐ or 3‐substituted, is an important scaffold, and despite its presence in several therapeutic agents, it is chemically unexploited. Furthermore, only a few examples in literature report this moiety in its enantiopure form. Here, taking advantage to the formation of diastereomeric amides by using (S)‐phenylethylamine, which show significant differences in terms of 1H‐nuclear magnetic resonance (NMR) spectra and other physical chemical properties, we defined for the first time the absolute configuration of each amide, both 2‐ or 3‐substituted. Moreover, the diastereomeric amides were further hydrolyzed in acid conditions, letting to the achievement of the corresponding 1,4‐benzoxathian carboxylic acids. [ABSTRACT FROM AUTHOR]

While not initially a focus or priority, in recent decades, an emphasis has been placed on the activity of individual enantiomers of widely used pesticides. Of particular note are organophosphorus‐based pesticides like fenamiphos and profenofos, as examples. This work explores the enantioselective high‐performance liquid chromatography (HPLC) separations of seven such organophosphorus pesticides (OP's) on the library of immobilized polysaccharide‐based chiral stationary phases (CSPs) with normal phase hexane/alcohol mixtures. Further exploration of the effect of mobile phase strength and temperature on several of the separations was performed using simple factorial design. Equivalent retention of the first eluting enantiomer of several combinations of temperature and mobile phase was compared for peak shape, selectivity, and resolution. Similarly, equivalent selectivity of several combinations of temperature and mobile phase was compared for peak shape, retention of the first eluting enantiomer, and resolution. The results of this study make available several new chiral separations of the OPs included in the work that were not previously documented, including separations on the three most recently commercialized phases, Chiralpak IH, IJ, and IK. Additionally, sufficient understanding was obtained to be able to predict the trade‐off of resolution, analysis time, peak sharpness (and thus improve limit‐of‐detection [LOD]/limit‐of‐quantification [LOQ]), robustness, and convenience of conditions for further application optimization. [ABSTRACT FROM AUTHOR]

The presence of planar chirality of a variety of medium‐sized heterocycles, along with nine‐membered cyclic ketone and its enol ester, was revealed by observation of isolable enantiomers by analytical high‐performance liquid chromatography (HPLC) using a chiral stationary phase with a polysaccharide‐based chiral selector. Several tens of milligrams of enantiomers of the planar‐chiral molecules were successfully separated by preparative‐scale HPLC, leading to the preparation of an enantioenriched sample. This in turn enabled detailed stereochemical studies, including measurement of half‐lives of the optical activity and X‐ray crystallography for elucidation of stereochemistry. [ABSTRACT FROM AUTHOR]

Recently we published in this journal an enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitative determination of 3,4-methylenedioxymethamphetamine (MDMA) and its major phase-1 metabolites, 4-hydroxy-3-methoxyamphetamine (HMA), 4-hydroxy-3-methoxymethamphetamine (HMMA) and 3,4-methylenedioxyamphetamine (MDA) in human plasma, sweat, oral fluid and urine. Since we did not achieve simultaneous enantioseparation of all 4 compounds with a single chiral column, two amylose-based chiral columns were used alternatively. Further optimization of the mobile phase in the present study enabled baseline separation of all four pairs of enantiomers on a single Lux AMP column. In addition, by optimization of the column dimension and applied flow-rate it became possible to complete the separation within 6 minutes. These new methods were applied to the analysis of human plasma, oral fluid and urine. While results on the concentration of MDMA and its metabolites in various biological fluids were reported in our recent publication, in the present study an attempt was made to hydrolyze glucuronides in urine samples by using alternatively, hydrochloric acid or glucuronidase and to evaluate the effect of hydrolysis on the concentration and enantiomeric distribution of hydroxy metabolites of MDMA such as HMA and HMMA. • Optimization of enantioselective method to quantify MDMA and some of its metabolites. • The method was applied to human plasma, oral fluid and urine. • The hydrolysis effect on MDMA hydroxylated metabolites was studied. [ABSTRACT FROM AUTHOR]

Abstract Background To explore the release behavior of ketoprofen enantiomers from alginate-metal-complexes. Five mathematical models of drug release kinetics were investigated. Results Beads of alginate-metal complexes, loaded with racemic ketoprofen, were prepared by the ionotropic method. Divalent (Ca, Ba, Zn) and trivalent (Fe, Al) metals were used in the preparation of single-metal and mixed-metal alginate complexes. In vitro release experiments were carried out in an aqueous phosphate buffer medium at pH = 7.4. The concentrations of ketoprofen released enantiomers were determined using chiral HPLC technique. The obtained data were used to simulate the release kinetic of ketoprofen enantiomers using various mathematical models. The Korsmeyer-Peppas model was the best fit for Ca, Al, and Fe beads. Moreover, alginate-iron beads tend to release the drug faster than all other cases. In contrast, the drug release for alginate-barium complex was the slowest. The presence of barium in alginate mixed-metal complexes reduced ketoprofen release in the case of Fe and Zn, while it increased the release in the case of Al complex. Conclusion In all the studied cases, ketoprofen showed very slow release for both enantiomers over a period exceeded 5 h (10 days in some cases). The release rate modification is possible using different multivalent metals, and it is also feasible by using two different metals for congealing either consecutively or simultaneously.

Stereogenic silicon centres in functionalised tetracoordinated organosilanes generally exhibit very high configurational stability under neutral conditions. This stability drops completely when higher coordination states of the silicon centre are reached due to rapid substituent exchange. Herein we describe the synthesis of chiral and neutral pentacoordinate silicon derivatives with high configurational stability. The zwitterionic nature of these air‐ and water‐tolerant species allows for the first time their direct and efficient optical resolution using chiral HPLC techniques. By means of this method, pentacoordinate silicon compounds exhibiting high Si‐inversion have been obtained as single enantiomers. A rationalisation of the enantiomerisation pathways has been also carried out using DFT calculations. [ABSTRACT FROM AUTHOR]

Racemic 2,3-dihydro-1H-inden-1-ols were resolved into enantiomers using kinetically controlled esterification of dihydroindenols by vinyl acetate with biocatalysis with Burkholderia cepacia lipase. The absolute configuration of halodihydroindenol enantiomers was defined by a convergent method of chiral HPLC analysis in combination with enzymatic analysis as well as single crystal X-Ray diffraction. The combined use of these methods increases the reliability in determining the absolute configurations of the studied compounds. [ABSTRACT FROM AUTHOR]

In the present study, an accurate, rapid, and simple chiral HPLC‐UV method with amylose tris(3‐chloro‐5‐methylphenylcarbamate) as stationary phase was developed and applied for enantiomeric determination of six nonsteroidal anti‐inflammatory drugs (NSAIDs) in the commercial pharmaceutical formulations, including (R,S)‐ibuprofen, S‐ibuprofen, (R,S)‐ketoprofen, S‐ketoprofen, S‐naproxen, and (R,S)‐loxoprofen sodium. Experiments on the influence of mobile phase composition, proportion of organic modifier, percentage of acid additives, and column temperature on enantioseparation were conducted to obtain the best separation condition. It was indicated that one mobile phase simply composed of acetonitrile‐water (0.1% formic acid, v/v) at the proportion of 50:50 (v/v) with a flow rate of 0.6 ml/min at 22°C could simultaneously provide the excellent enantiomeric resolutions for all selected NSAIDs, which made the enantioseparation process more applicable and operable. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Calibration curve of each enantiomer at the concentration of 5.0–100 ug/ml showed good linearity with the correlation coefficient above 0.9996. Satisfactory recovery (96.54–101.54%), good intra‐day precision (RSD 0.52–1.46%), and inter‐day precision (RSD 0.13–1.09%) were also obtained. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Quantitative results of the commercial capsules and tablets demonstrated that the difference between the declared and measured values did not exceed 1.52%. [ABSTRACT FROM AUTHOR]

Four enantiomeric forms of natural prostaglandins, ent-PGF2α ((−)-1), ent-PGE2 ((+)-2) ent-PGF1α ((−)-3), and ent-PGE1 ((+)-4) have been synthetized in gram scale by Corey synthesis used in the prostaglandin plants of CHINOIN, Budapest. Chiral HPLC methods have been developed to separate the enantiomeric pairs. Enantiomers of natural prostaglandins can be used as analytical standards to verify the enantiopurity of synthetic prostaglandins, or as biomarkers to study oxidation processes in vivo.

Cocoa and chocolate antioxidants might contribute to human health through, for instance, blood flow improvement or blood pressure and glycemia reduction, as well as cognitive function improvement. Unfortunately, polyphenol content is reduced during cocoa fermentation, drying, roasting and all the other phases involved in the chocolate production. Here, we investigated the evolution of the polyphenol content during all the different steps of chocolate production, with a special emphasis on roasting (3 different roasting cycles with 80, 100, and 130 °C as maximum temperature). Samples were followed throughout all processes by evaluating the total polyphenols content, the antioxidant power, the epicatechin content, and epicatechin mean degree of polymerization (phloroglucinol adducts method). Results showed a similar trend for total polyphenol content and antioxidant power with an unexpected bell-shaped curve: an increase followed by a decrease for the three different roasting temperatures. At the intermediate temperature (100 °C), the higher polyphenol content was found just after roasting. The epicatechin content had a trend similar to that of total polyphenol content but, interestingly, the mean degree of polymerization data had the opposite behavior with some deviation in the case of the highest temperature, probably due to epicatechin degradation. It seems likely that roasting can free epicatechin from oligomers, as a consequence of oligomers remodeling.

We recently identified 6-nitrodopamine and other nitro-catecholamines (6-nitrodopa, 6-nitroadrenaline), indicating that the endothelium has the ability to nitrate the classical catecholamines (dopamine, noradrenaline, and adrenaline). In order to investigate whether drugs could be subject to the same nitration process, we synthesized 4-nitro- and 7-nitropropranolol as probes to evaluate the possible nitration of the propranolol by the endothelium. The separation of the enantiomers in very high yields and excellent enantiopurity was achieved by chiral HPLC. Finally, we used Riguera’s method to determine the absolute configuration of the enantiomers, through double derivatization with MPA and NMR studies.

Imazamox (IMX), a chiral herbicide used in cereals and oilseed crops to control weeds, is commonly sold as a racemic mixture. Its enantiomers, being chiral compounds, may exhibit unique properties when exposed to chiral environments. While IMX enantiomers have been reported to degrade differently in soil and be toxic to some species, their effects on human systems remain poorly understood. This study utilized Caco-2 (human colon adenocarcinoma cell line) cells to assess the in vitro permeability of a racemic mixture of IMX and its isolated enantiomers. Additionally, the study aimed to evaluate whether the metabolite imazamox-O-desmethyl (IMX-D) forms during the permeability process. An enantioselective chromatographic method was developed, fully validated, and the apparent permeability values were obtained. The apparent permeability of rac-IMX, (+)-IMX, and (-)-IMX was determined to be 4.15 × 10 -5 , 5.78 × 10 -5 , and 7.33 × 10 -5  cm s -1 , respectively. These findings suggest that IMX exhibits high intestinal permeability, with an enantioselective absorption for (-)-IMX as compared to (+)-IMX. Finally, the permeability study in Caco-2 cells revealed that the metabolite IMX-D was not generated., (© 2024 Wiley‐VCH GmbH.)

One has to keep in mind that Crownpak CR(+) column reports a slightly decreased EP value, and the Chirobiotic T column displays a slightly increased EP value in comparison to the true value. EP is an important quality control parameter which must be adhered to for SP 11 sp C and SP 18 sp F-labelled amino acid RP production and determined by chiral HPLC or TLC methods. Keywords: 18F and 11C-labelled amino acid; chiral HPLC; enantiomeric purity; quality control of PET radiopharm-aceuticals EN 18F and 11C-labelled amino acid chiral HPLC enantiomeric purity quality control of PET radiopharm-aceuticals 861 866 6 01/27/22 20211101 NES 211101 1 Introduction Amino acids are fundamental biomolecular building blocks which play significant roles in human metabolism, such as protein synthesis, neurotransmitter biosythesis, and hormonal metabolism. [Extracted from the article]

BACKGROUND: The determination of enantio‐separation, absolute configuration and chiral recognition mechanism of ofloxacin and flumequine was carried out by high‐performance liquid chromatography (HPLC) and modeling studies. The column used was a Chiralcel OD‐H with normal and polar organic mobile phase modes. The exhaustive chiral separation was optimized through various HPLC parameters. RESULTS: The selectivity, separation factors and resolution factors for ofloxacin were 8.2 and 9.4, 1.15 and 2.43 in the normal mobile phase, while these values were 10.5 and 12.0, 1.14 and 2.40 for flumequine in polar organic mobile phase mode, respectively. The thermodynamic parameters were ΔH (−0.137 J mol−1), ΔS (7.35 × 10−4 J mol−1) and ΔG (−0.360 J mol−1 K−1) for ofloxacin, and ΔH (−0.035 J.mol−1), ΔS (21.3 × 10−4 J mol−1) and ΔG (−0.105 J mol−1 K−1) for flumequine, confirming spontaneous chiral separation at all temperatures. The chiral recognition mechanism was established by HPLC and modeling results. The modeling binding affinity were −2.5 kcal mol–1 (R‐enantiomer) and −2.6 kcal mol–1 (S‐enantiomer) for ofloxacin, and −2.30 kcal mol–1 (R‐enantiomer) and −2.40 kcal mol–1 (S‐enantiomer) for flumequine enantiomers. The chiral resolution is controlled by hydrogen bonding, π–π interactions and other forces. CONCLUSION: These methods were applied to monitor ofloxacin and flumequine quinolones in urine samples. Briefly, the developed chiral HPLC methods are effective and may be used to analyze the reported enantiomers in any biological sample. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Series of chiral palladium(II) allyl and cinnamyl complexes bearing a C1‐symmetric N‐heterocyclic carbenes were synthesized from achiral precursors. The chirality of theses complexes results from the formation of the carbene‐palladium bond which restricts the rotation of dissymmetric N‐aryl substituents of the NHC and thus creates an axis of chirality. Chiral HPLC at preparative scale enabled the resolution of racemic complexes and provided a straightforward access to complexes with excellent enantiopurities (>99.5% ee). Enantiopure complexes were studied by crystal X‐ray diffraction and electronic circular dichroism (ECD). Their configuration stabilities were investigated both experimentally and theoretically through the determination of the rotational barrier values. These complexes were tested for the intramolecular α‐arylation of amides, with a moderate chiral induction (up to 54% ee). [ABSTRACT FROM AUTHOR]

Stereoselectivity is well known and very pronounced in drug metabolism and receptor binding. However, much less is known about stereoselectivity in drug membrane transport. Here, we characterized the stereoselective cell uptake of chiral phenylethylamine derivatives by human monoamine transporters (NET, DAT, and SERT) and organic cation transporters (OCT1, OCT2, and OCT3). Stereoselectivity differed extensively between closely related transporters. High-affinity monoamine transporters (MATs) showed up to 2.4-fold stereoselective uptake of norepinephrine and epinephrine as well as of numerous analogs. While NET and DAT preferentially transported (S)-norepinephrine, SERT preferred the (R)-enantiomer. In contrast, NET and DAT showed higher transport for (R)-epinephrine and SERT for (S)-epinephrine. Generally, MAT stereoselectivity was lower than expected from their high affinity to several catecholamines and from the high stereoselectivity of some inhibitors used as antidepressants. Additionally, the OCTs differed strongly in their stereoselectivity. While OCT1 showed almost no stereoselective uptake, OCT2 was characterized by a roughly 2-fold preference for most (R)-enantiomers of the phenylethylamines. In contrast, OCT3 transported norphenylephrine and phenylephrine with 3.9-fold and 3.3-fold preference for their (R)-enantiomers, respectively, while the para-hydroxylated octopamine and synephrine showed no stereoselective OCT3 transport. Altogether, our data demonstrate that stereoselectivity is highly transporter-to-substrate specific and highly diverse even between homologous transporters.

Herein, we report a simple and efficient approach to synthesize a functionalized 2,18‐dimethoxy‐5,10,15‐trioxa[9]helicene. It was synthesized from simple phenol building blocks using two subsequent reactions namely oxidative coupling and dehydrative cyclization or palladium mediated cyclization. The molecular integrity of the helical core was determined by single‐crystal X‐ray diffraction and NMR techniques. Its crystal structure showed the spontaneous resolution which was attributed to the conglomerate formation of the same helical isomer via C−H⋅⋅⋅O and π⋅⋅⋅π or H⋅⋅⋅π interactions. Then, it was converted to racemic 2,18‐dihydoxy‐5,10,15‐trioxa[9]helicene. Enantiomers were separated on preparative HPLC with high optical purity (>99 % ee). Based on electronic circular dichroism, the absolute configurations of dextrorotary and levorotatory antipodes were assigned as P and M, respectively. We also studied the absorption, emission and chiroptical behavior of these helical compounds in the solution state. [ABSTRACT FROM AUTHOR]

Starting from methyl cycloheptatrienyl-1-carboxylate, 6-acylation was successfully achieved employing glutaryl chloride in the presence of AlCl3 under controlled reaction conditions to furnish keto carboxylic acid product. After protection of this keto carboxylic acid as tert -butyl ester, reagent-controlled enantioselective reductions delivered configuration-defined methyl-6-hydroxylalkyl cycloheptatriene-1-carboxylates with up to 80% ee. Whereas simple NaBH4 reduction of the keto carboxylic acid and subsequent lactonization afforded a methyl-6-tetrahydropyranonyl cycloheptatriene-1-carboxylate. Resolution using chiral HPLC delivered the product enantiomers with up to >99% ee Finally, ECD analyses enabled structure elucidation. The products are used as key intermediates in enantioselective 6,11-methylene-lipoxin B4 syntheses. [ABSTRACT FROM AUTHOR]

Amino acids are key building blocks for the synthesis of chiral organic materials. In this context, -azido amino acids are interesting starting materials which allow the construction of functionalized, amino-acid based compounds by copper-catalyzed alkyne-azide click reactions. We have now employed this strategy for the synthesis of arginine-derivatives and found that the formation of the azide and the click reaction can be carried out in good yields and with almost no loss of stereopurity. However, further transformation by saponification/amide-formation led to significant racemization at the -carbon. This process was investigated in detail, showing that the triazole-moiety seems to be responsible for the facile racemization. Thus, the highly useful modification of -azido amino acids by the CuAAC-reaction needs to be used with caution when stereopure materials are desired. [ABSTRACT FROM AUTHOR]

Starting from methyl cycloheptatrienyl-1-carboxylate, 6-acylation was successfully achieved employing glutaryl chloride in the presence of AlCl3 under controlled reaction conditions to furnish keto carboxylic acid product. After protection of this keto carboxylic acid as tert -butyl ester, reagent-controlled enantioselective reductions delivered configuration-defined methyl-6-hydroxylalkyl cycloheptatriene-1-carboxylates with up to 80% ee. Whereas simple NaBH4 reduction of the keto carboxylic acid and subsequent lactonization afforded a methyl-6-tetrahydropyranonyl cycloheptatriene-1-carboxylate. Resolution using chiral HPLC delivered the product enantiomers with up to >99% ee Finally, ECD analyses enabled structure elucidation. The products are used as key intermediates in enantioselective 6,11-methylene-lipoxin B4 syntheses. [ABSTRACT FROM AUTHOR]

The enantioseparation of four phthalimide derivatives (thalidomide, pomalidomide, lenalidomide and apremilast) was investigated on five different polysaccharide-type stationary phases (Chiralpak AD, Chiralpak AS, Lux Amylose-2, Chiralcel OD and Chiralcel OJ-H) using neat methanol (MeOH), ethanol (EtOH), 1-propanol (PROP), 2-propanol (IPA) and acetonitrile (ACN) as polar organic mobile phases and also in combination. Along with the separation capacity of the applied systems, our study also focuses on the elution sequences, the effect of mobile phase mixtures and the hysteresis of retention and selectivity. Although on several cases extremely high resolutions (Rs > 10) were observed for certain compounds, among the tested conditions only Chiralcel OJ-H column with MeOH was successful for baseline-separation of all investigated drugs. Chiral selector- and mobile-phase-dependent reversals of elution order were observed. Reversal of elution order and hysteresis of retention and enantioselectivity were further investigated using different eluent mixtures on Chiralpak AD, Chiralcel OD and Lux Amylose-2 column. In an IPA/MeOH mixture, enantiomer elution-order reversal was observed depending on the eluent composition. Furthermore, in eluent mixtures, enantioselectivity depends on the direction from which the composition of the eluent is approached, regardless of the eluent pair used on amylose-based columns. Using a mixture of polar alcohols not only the selectivities but the enantiomer elution order can also be fine-tuned on Chiralpak AD column, which opens up the possibility of a new type of chiral screening strategy.

The enantiomeric separation of 15 racemic 4-aryl-3,4-dihydropyrimidin-2(1H)-one (DHP) alkoxycarbonyl esters, some of which proved to be highly active as A2B adenosine receptor antagonists, was carried out by HPLC on ChirobioticTM TAG, a chiral stationary phase (CSP) bearing teicoplanin aglycone (TAG) as the chiral selector. The racemic compounds were separated under polar organic (PO) conditions. Preliminarily, the same selectands were investigated on three different Pirkle-type CSPs in normal-phase (NP) conditions. A baseline separation was successfully obtained on TAG-based CSPs for the majority of compounds, some of which achieved high enantioselectivity ratios (α > 2) in contrast with the smaller α values (1–1.5) and the lack of baseline resolution observed with the Pirkle-type CSPs. In particular, the racemic tetrazole-fused DHP ester derivatives, namely compounds 8 and 9, were separated on TAG-based HPLC columns with noteworthy α values (8.8 and 6.0, respectively), demonstrating the potential of the method for preparative purposes. A competition experiment, carried out with a racemic analyte (6) by adding N-acetyl-d-alanine (NADA) to the mobile phase, suggested that H-bonding interactions involved in the recognition of the natural dipeptide ligand d-Ala-d-Ala into the TAG cleft should be critical for enantioselective recognition of 4-aryl DHPs by TAG. The X-ray crystal structure of TAG was elucidated at a 0.77 Å resolution, whereas the calculation of molecular descriptors of size, polar, and H-bond interactions, were complemented with molecular docking and molecular dynamics calculations, shedding light on repulsive (steric effects) and attractive (H-bond—polar and apolar) interactions between 4-aryl DHP selectands and TAG chiral selectors.

A facile, multicomponent (MCR) atom-economic synthesis of novel spiro-oxindolo pyrrolizidine adducts of piperine has been achieved via an intermolecular 1,3-dipolar azomethine ylide cycloaddition reaction. Either of the two conjugated double bonds in piperine takes part in the reaction to produce two regioisomeric adducts in racemic form. Acenaphthoquinone, ninhydrin and different isatin derivatives were reacted with proline and piperine to afford a never before reported library of 22 compounds. The structures of the products were determined by 1D/2D NMR, mass spectral analysis and confirmed by X-ray crystallography of selected products. Chiral HPLC separation was performed to measure the specific rotation and CD spectra of the enantiomers for two racemic compounds. [ABSTRACT FROM AUTHOR]

An efficient first total synthesis of highly polar ulmoside A and (2 R ,3 R)-taxifolin-6- C -β- d -glucopyranoside, useful for the prevention of metabolic disorders, has been described. Key elements of the synthesis include a Sc(OTf)3-catalyzed regio- and stereoselective C -glycosidation on taxifolin in 35% yield with d -glucose and chiral semipreparative reverse-phase high-performance liquid chromatography (HPLC) for the separation of both taxifolins and the diastereomeric mixture of taxifolin-6- C -β- d -glucopyranosides. Correlation of the analytical data of synthetic ulmoside A and its diastereomer with a natural ulmoside A sample confirmed the assigned absolute stereochemistry of the natural products. [ABSTRACT FROM AUTHOR]

A new high‐performance liquid chromatography (HPLC) method for separation and determination of panthenol enantiomers in hair care products was developed. Two types of detectors, low‐wavelength ultraviolet (UV) and polarimetric, were used. Optimized conditions consisted of coupled achiral, amino type, and chiral, amylose tris(3,5‐dimethylphenylcarbamate), stationary phases, mixture of n‐hexane/ethanol (60:40, v/v) as mobile phase under isocratic conditions and flow rate 0.8 cm3 min−1. The effect of column temperature on retention and resolution of enantiomers was studied. The analysis runtime was 10 minutes, and the average retention times for d‐ and l‐panthenol were 7.10 ±0.1 minutes and 8.21 ±0.2 minutes, respectively. The resolution of enantiomers on coupled achiral‐chiral columns was Rs = 2.7. The solid‐phase extraction method was employed for extraction and purification of analytes. The validated method was selective, accurate, and linear (R2 >.998) over the concentration range of 0.001 to 1.0 mg cm−3 for both enantiomeric forms. The limits of detection (LOD) and quantitation (LOQ) of each enantiomer were 0.3 and 1.0 μg cm−3, respectively. The results demonstrated the occurrence of d‐panthenol in hair care products. [ABSTRACT FROM AUTHOR]

• Borrowing hydrogen reaction using the benzylPd(II) system. • Direct use of 2-aminobenzyl alcohol for construction of quinazoline 2. • Self-condensation of in-situ generated 2-aminobenzaldehyde followed by hydrogen transfer. • Both enantiomers are available after chiral separation of 2. We demonstrate the borrowing hydrogen reaction of readily available 2-aminobenzyl alcohol 1 , which is a new synthetic strategy for the construction of ring-fused quinazoline systems. The cascade reaction involves the dehydrogenative oxidation of alcohol 1 to the corresponding aldehyde 3 followed by self-condensation and reduction utilizing the benzyl Pd(II) system. The racemate 2 was successfully separated by chiral HPLC, affording a pair of enantiomers with high purity (>99 % ee) in a 1:1 ratio. The absolute configuration of one enantiomer was established via X-ray crystallography of its heavy atom analog. The structures of the racemate 2 and the pure enantiomer 2a were characterized by single-crystal X-ray analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

In the present study enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were developed for the quantitative determination of 3,4-methylenedioxy-methamphetamine (MDMA) and its major phase-1 metabolites 4-hydroxy-3-methoxyamphetamine (HMA), 4-hydroxy-3-methoxymethamphetamine (HMMA) and 3,4-methylenedioxyamphetamine (MDA) in human plasma, sweat, oral fluid (OF) and urine. The simultaneous separation of all these compounds and their respective enantioseparation was accomplished on two polysaccharide-based chiral columns. The Lux AMP column with a proprietary chiral selector enabled baseline separation of the enantiomers of MDMA, HMA and HMMA while MDA enantiomers could not be separated with this column under the experimental conditions used in this study. The Lux i-Amylose-3 column based on amylose tris(5-chloro-3-methylphenylcarbamate) as chiral selector baseline-separated the enantiomers of MDMA, HMMA and MDA while the enantiomers of HMA could not be separated. Thus, the various samples were analyzed by using both columns alternatively in combinations with acetonitrile containing 25% (v/v) 5 mM ammonium bicarbonate buffer at pH 11.0 as mobile phase. Analysis time was less than 4 min with the Lux AMP column and less than 6 min with the Lux i-Amylose-3 column. Both methods were validated and applied to the enantioselective determination of MDMA and its phase-I metabolites in human biological fluids, and enantioselective metabolism of MDMA was confirmed. • An enantioselective method for quantitative determination of MDMA and some of its metabolites in human biological fluids. • The method is simple and fast, allowing high-throughput analyses. • The method was applied for the enantioselectivity in metabolism and pharmacokinetic of the parent compound and metabolites. [ABSTRACT FROM AUTHOR]

In the pharmaceutical industry, the analysis of atropisomers is of considerable interest from a scientific and regulatory perspective. The compound of interest contains two stereogenic axes due to the hindered rotation around the single bonds connecting the aryl groups, which results in four potential configurational isomers (atropisomers). The separation of the four atropisomers is achieved on a derivatized β-cyclodextrin bonded stationary phase. Further investigation shows that low temperature conditions, including sample preparation (−70 °C), sample storage (−70 °C), and chromatographic separation (6 °C), were critical to preventing interconversion. LC-UV-Laser Polarimetric analysis identified peak 1/2 as a pair of enantiomers and peak 3/4 as another. Thermodynamic analysis of the retention data indicated that the separation of the pairs of enantiomers is primarily enthalpy controlled as indicated by the positive slope of the van’t Huff plot. The difference in absolute Δ (Δ H), ranged from 2.20 kJ/mol to 2.42 kJ/mol.

The synthetic cannabinoid MDMB-CHMCZCA was characterized by various spectroscopic techniques including NMR spectroscopy and tandem mass spectrometry. The synthetic sample was found to be of S-configuration by VCD spectroscopy and comparison of the data with DFT calculations, while ECD spectroscopy was found to be inconclusive in this case. The enantiomeric purity of samples from test purchases and police seizures was assessed by a self-developed chiral HPLC method.

Twenty natural-product-like 2,8-dioxabicyclo[3.3.1]nonane derivatives were synthesized and their neuroprotective activities were tested using human monoamine oxidases (MAO) A and B and acetyl and butyryl cholinesterases (ChE). Compound 1s showed inhibitory activity for MAO-A, MAO-B and acetylcholinesterase (AChE) (IC 50 values 34.0, 2.3 and 11.0 µM, respectively). The inhibition mode of (-)-1s for MAO-B was investigated. Chiral HPLC of (±)-1s separated the enantiomers and (-)-1s showed MAO-B inhibitory activity. Molecular docking simulation of (-)-1s and MAO-B revealed the binding mode.

A novel, fast and sensitive enantioselective HPLC assay with a new core–shell isopropyl carbamate cyclofructan 6 (superficially porous particle, SPP) chiral column (LarihcShell-P, LSP) was developed and validated for the enantiomeric separation and quantification of verapamil (VER) in rat plasma. The polar organic mobile phase composed of acetonitrile/methanol/trifluoroacetic acid/triethylamine (98:2:0.05: 0.025, v/v/v/v) and a flow rate of 0.5 mL/min was applied. Fluorescence detection set at excitation/emission wavelengths 280/313 nm was used and the whole analysis process was within 3.5 min, which is 10-fold lower than the previous reported HPLC methods in the literature. Propranolol was selected as the internal standard. The S-(−)- and R-(+)-VER enantiomers with the IS were extracted from rat plasma by utilizing Waters Oasis HLB C18 solid phase extraction cartridges without interference from endogenous compounds. The developed assay was validated following the US-FDA guidelines over the concentration range of 1–450 ng/mL (r2 ≥ 0.997) for each enantiomer (plasma) and the lower limit of quantification was 1 ng/mL for both isomers. The intra- and inter-day precisions were not more than 11.6% and the recoveries of S-(−)- and R-(+)-VER at all quality control levels ranged from 92.3% to 98.2%. The developed approach was successfully applied to the stereoselective pharmacokinetic study of VER enantiomers after oral administration of 10 mg/kg racemic VER to Wistar rats. It was found that S-(−)-VER established higher Cmax and area under the concentration-time curve (AUC) values than the R-(+)-enantiomer. The newly developed approach is the first chiral HPLC for the enantiomeric separation and quantification of verapamil utilizing a core–shell isopropyl carbamate cyclofructan 6 chiral column in rat plasma within 3.5 min after solid phase extraction (SPE).

The five‐steps synthesis of a hemicryptophane cage combining a benzene‐1,3,5‐tricarboxamide unit and a cyclotriveratrylene (CTV) moiety is described. Chiral high‐performance liquid chromatography (HPLC) was used to resolve the racemic mixture. The absolute configuration of the isolated enantiomers was assigned by comparison of the experimental electronic circular dichroism (ECD) spectra with the calculated ones. X‐ray molecular structures reveal that the capped benzene‐1,3,5‐tricarboxamide unit adopts a structurally chiral conformation in solid state: the chirality of CTV moiety controls the Λ or Δ orientation of the three amides. [ABSTRACT FROM AUTHOR]