Chirality最新文献

Electrons in circular motion emit electromagnetic radiation and lose their energy and angular momentum, both of which are carried away by the radiation field. Electromagnetic radiation from such electrons is not only circularly polarized but also, in general, possessing helical phase structure, the former of which corresponds to spin angular momentum and the latter orbital angular momentum. Based on the classical electrodynamics, we show that the chiral topological property related to the orbital angular momentum arises from deformation of the electromagnetic field due to the relativistic effect.

Each year, new psychoactive substances appear on the global drug market leading to constant changes. Most of these compounds with stimulating effect possess a chiral center, thus leading to two enantiomers with presumably different pharmacological properties. Among them, synthetic cathinones, often misleadingly traded as “bath salts,” play an important role. There is little knowledge about the distinct effect of the enantiomers. The aim of this study was to test a commercially available Lux® i-Amylose-3 column by HPLC-UV for enantiorecognition of cathinone derivatives. Overall, 80 compounds were tested in normal phase mode, where 75 substances were separated under initial conditions. After method optimization, at least partial separation was achieved for the remaining compounds. The same set of substances was measured in polar-organic mode, where 63 analytes were resolved into their enantiomers under initial conditions with very short retention times. Both modes showed complementary results for the individual compounds. Furthermore, the tested methods proved to be suitable for differentiation of positional isomers, which can be useful for drug checking programs. All measurements were carried out under isocratic conditions, and intraday and interday repeatability tests were performed.

The aim of this study was to investigate the chiral inversion and the stereoselective pharmacokinetic profiles of desmethyl-phencynonate hydrochloride after administration of the single isomer and its racemate to beagle dogs. A liquid chromatography with tandem mass spectrometry (LC–MS/MS) method was established for determination of the stereoisomers on chiral columns in beagle dog plasma, which met all the requirements. The chiral inversion in dogs of the desmethyl-phencynonate hydrochloride were studied after administration of the single isomer or the racemic modification. The stereoselective pharmacokinetic profiles of the desmethyl-phencynonate hydrochloride were studied by assays for simultaneous isomers after administration of the racemic modification. The results showed that the absorption of the R­configuration dosed as the single isomer was higher than it dosed as the racemic modification. The AUC_(0-t), AUC_(0-∞), and C_max of the S­configuration were much higher than those of R­configuration after oral administration of the racemic desmethyl-phencynonate hydrochloride. The chiral inversion of desmethyl-phencynonate isomers could not occur in dogs after administration of the R­configuration.

The absolute configuration of three chiral eugenol derivatives was assigned by a multi-step methodology based on enantioselective HPLC combined with spectroscopic and theoretical calculations. Milligram amounts of enantiopure forms used for stereochemical characterization were isolated by HPLC on the immobilized amylose-based chiral stationary phase Chiralpak IG using normal phase elution conditions. The absolute configuration was indirectly determined for one of the three compounds by ¹H NMR via methoxy-α-trifluoromethyl-α-phenylacetic acid derivatization (Mosher's acid). Comparison of the experimental and predicted electronic circular dichroism spectra confirmed the stereochemical assignment by Mosher's method and extended the absolute configuration assignment to two other chiral compounds.

Among different substance classes, New Psychoactive Substances (NPS) comprise chiral amphetamines for stimulant and empathic effects. There is little knowledge in terms of clinical studies about possibly different effects of the two enantiomers of novel amphetamine derivatives. For this reason, there is a big demand for enantioseparation method development of this new substance class.

Regarding gas chromatography, cyclodextrins proved to be effective for enantioseparation of NPS. In our attempt, an Astec® Chiraldex™ G-PN column containing 2,6-di-O-pentyl-3-propionyl-γ-cyclodextrin and a Lipodex™ D column containing heptakis-(2,6-di-O-pentyl-O-acetyl)-β-cyclodextrin as chiral selector served as stationary phases in a Shimadzu GCMS-QP2010 SE system.

Because of the special coating, maximum temperature is limited to 200 °C isothermal or 220 °C in programmed mode. To ensure detection, trifluoroacetic anhydride (TFAA) was used to increase sample volatility.¹ As a result, 35 amphetamines were tested as their TFAA-derivatives.

A screening method with a temperature gradient from 140 °C to 200 °C at a heating ramp of 1 °C per minute and final time of 5 min, showed baseline separation for seven and partial separations for 16 trifluoro acetylated amphetamines using the Chiraldex™ G-PN column. Six baseline and nine partial separations were observed with the Lipodex™ D column, respectively.

Metal clusters have drawn considerable research attention over the years due to their fascinating optical properties. Owing to their appealing photophysical characteristics, these materials have drawn attention as potential candidates for various application in diverse fields, including disease detection, biosensing, chemical sensing, and the fabrication of light-harvesting materials. Presently, there is an increasing research focus on the use of clusters in biomedical research, both as biodetection platform and as bioimaging agents. Of special interest are chiral clusters, which can selectively interact with chiral biomolecules owing to their optical activity. Herein, we showcase the use of a pair of chiroptically active copper clusters for the enantioselective detection of lysine, an amino acid of vast biological relevance. Two techniques are concurrently employed for the detection of lysine at varying concentrations. Circular dichroism serves as a potent tool for detecting lysine at low concentrations, whereas luminescence is effectively employed as a detection method for high analyte concentrations. The combined electronic impact of clusters and lysine resulted in the emergence of an enhanced enantioselective Cotton effect at specific wavelength.

This study describes the interaction of human serum albumin (HSA) with the binol derivative (R)-(+)-3,3′-dibromo-1,1′-bi-2-naphthol (R-BrB), which has its optical activity based on the prohibitive energetic barrier for conversion into the enantiomer (S)-(+)-3,3′-dibromo-1,1′-bi-2-naphthol (S-BrB). The objective was to assess the ability of HSA to differentiate axial enantiomers based on their binding efficiency and their impact on the CD spectra. We discovered that both enantiomers were effective ligands, and the CD signal disappeared when equimolar amounts of R-BrB and S-BrB were simultaneously added, indicating no preference for either enantiomer. The complexation resulted in a significant signal increase at 250 nm and a bathochromic effect at 370 nm. Molecular docking simulations were performed, and the lower energy pose of R-BrB was selected for DFT calculations. The theoretical CD spectra of free and complexed R-BrB were obtained and showed alterations corroborating the experimental results. By comparing the difference spectrum (HSA:R-BrB minus HSA) with the spectrum of free RBrB in water or ethyl alcohol, we concluded that the CD signal intensification was due to the increased solubilization of R-BrB upon binding to HSA.

The separation of chiral drugs continues to pose a significant challenge. However, in recent years, the emergence of membrane-based chiral separation has shown promising effectiveness due to its environmentally friendly, energy-efficient, and cost-effective characteristics. In this study, we prepared chiral composite membrane via interfacial polymerization (IP), utilizing β-cyclodextrin (β-CD) and piperazine (PIP) as mixed monomers in the aqueous phase. The chiral separation process was facilitated by β-CD, serving as a chiral selective agent. The resulting membrane were characterized using SEM, FT-IR, and XPS. Subsequently, the chiral separation performance of the membrane for DL-tryptophan (Trp) was investigated. Lastly, the water flux, dye rejection, and stability of the membrane were also examined. The results showed that the optimized chiral PIP_0.5β-CD_0.5 membrane achieved an enantiomeric excess percentage (ee%) of 43.0% for D-Trp, with a solute flux of 66.18 nmol·cm⁻²·h⁻¹, and maintained a good chiral separation stability. Additionally, the membrane demonstrated positive performance in the selective separation of mixed dyes, allowing for steady operation over a long period of time. This study offers fresh insights into membrane-based chiral separations.

The adjustment of the main helical scaffold in helicenes is a fundamental strategy for modulating their optical features, thereby enhancing their potential for diverse applications. This work explores the influence of helical elongation (n = 5–9) on the structural, photophysical, and chiroptical features of symmetric oxa[n]helicenes. Crystal structure analyses revealed structural variations with helical extension, impacting torsion angles, helical pitch, and packing arrangements. Through theoretical investigations using density functional theory (DFT) calculations, the impact of helical extension on aromaticity, planarity distortion, and heightened chiral stability were discussed. Photophysical features were studied through spectrophotometric analysis, with insights gained through time-dependent DFT (TD-DFT) calculations. Following optical resolution via chiral high-performance liquid chromatography (HPLC), the chiroptical properties of both enantiomers of oxa[7]helicene and oxa[9]helicene were investigated. A slight variation in the main helical scaffold of oxa[n]helicenes from [7] to [9] induced an approximately three-fold increase in dissymmetry factors with the biggest values of|g_lum| of oxa[9]helicene (2.2 × 10⁻³) compared to|g_lum|of oxa[7]helicene (0.8 × 10⁻³), findings discussed and supported by TD-DFT calculations.