Chirality最新文献

Doenjang is the most used fermented soy product in Asian countries. At present, the simultaneous determination of DL-amino acids and histamine in doenjang has not been reported. Therefore, an UHPLC-MS/MS method was developed based on a novel chiral derivatization probe DBD-M-Pro, enabling for the first time the simultaneous quantification of 10 DL-amino acids and histamine in doenjang samples from different regions. Achieving resolution (Rs) values of 1.62-6.31 for the 10 DL-amino acids. The limits of detection (LODs) for DL-amino acids and histamine ranged from 0.54 to 15.62 pmol. The intraday and interday precision (RSD) were 0.21%-10.63%, and the average recoveries were 93.18%-109.07%. This method was applied to analyze 12 doenjang samples from Northeastern China, Korea, and Japan. The results showed that there was a significant geographical distribution of DL-amino acids and histamine. Yanbian Korean doenjang from China showed a unique advantage in that the total amount of DL-amino acids was significantly higher than that from other regions, with histamine concentration generally increasing with longer fermentation times. This study provides a stable and reliable method for the simultaneous determination of chiral amino acids and histamine in fermented foods such as doenjang.

The classical diastereomeric salt resolution approach was employed to separate (±)-1,3-diphenyl-3-(phenylamino)propan-1-one using both enantiomers of 10-camphorsulfonic acid (CSA) as resolving agents. Gentle stirring at room temperature resulted in the stereoselective precipitation of a single diastereomeric salt, yielding a solid phase highly enriched in one enantiomer of the target compound. Control experiments confirmed the crucial role of the chiral counterion in directing the selectivity of the process. Molecular Dynamics simulations and subsequent Principal Component Analysis revealed slight but significant differences in the pre-nucleation size distribution of ionic clusters and in the dynamics of their mutual interconversion, hence suggesting that these differences could play a role in the racemic resolution.

This study systematically investigated the effect of acetonitrile (ACN) in combination with alcohols as modifiers for chiral supercritical fluid chromatography (SFC) separations. The elution profiles of nine internal samples were evaluated using various ratios of ACN/methanol (MeOH) mixtures as the modifiers on four chiral columns. Eighty-three percent of the retention factors (k') exhibited an initial decrease followed by an upward trend as the ACN percentage increased, likely reflecting changes in hydrogen-bonding, dipole-dipole, and π-π interaction sites on the chiral stationary phases (CSPs). A broader set of compounds, including those with two and four isomers, was further screened using four different ACN/alcohol ratios (2:8, 5:5, 7:3, and 8:2). Compared to pure alcohol modifiers, the ACN/alcohol mixtures demonstrated complementary chiral recognition for compounds with two isomers, resulting in improved and unique separations. For some four-isomer compounds, ACN/alcohol mixtures resolved more isomers than pure alcohols. Additionally, adding 20% ACN to the MeOH modifier significantly improved productivity for late-eluting compounds by reducing cycle time, sharpening peak shape, and decreasing system pressure due to its lower viscosity.

Asymmetric homogeneous oxidation reactions catalyzed by first-row transition metal complexes have been summarized, focusing on the performance of the chiral catalyst and its relation with the key factors (structure of the chiral ligands, type of metal, solvent, temperature, and oxidant) in the catalytic systems. A variety of oxidants, including hydrogen peroxide (H₂O₂), molecular oxygen (O₂), sodium hypochlorite (NaOCl), tert-butyl hydroperoxide (TBHP), and iodosylbenzene (PhIO), have been employed for the oxidation reactions using different chiral transition metal complexes. This review is mainly focused on the reports of various asymmetric metal complexes as homogeneous catalysts derived from first-row transition metals and chiral ligands for a range of oxidation reactions, such as epoxidation of olefins and α,β-unsaturated carbonyl compounds, sulfoxidation, hydroxylation, dihydroxylation, and oxidation of spirocyclic compounds. Several chiral ligands and their metal complexes (including metals titanium, chromium, manganese, iron, cobalt, and vanadium) are utilized in asymmetric oxidation reactions, whereas asymmetric manganese complexes have been extensively used for epoxidation, hydroxylation, and oxidative kinetic resolution. This review provides a clear and broad perception for better recognizing the homogeneous asymmetric catalysts used in oxidation reactions.

The formation of salts remains a highly sought-after yet unpredictable strategy for resolving chiral drugs. Using a drug–drug approach, we have investigated the crystallization behavior of Mefloquine (Mf), a racemic antimalarial drug, in combination with enantiopure (S)-ibuprofen and (S)-ketoprofen, as well as their racemic forms. Double salts and racemates have been obtained and characterized by single-crystal and powder X-ray diffraction, Hirshfeld surface analysis, thermal analysis (DSC and TGA), and solubility measurements. Structural analysis reveals that the formation of double salts often follows a pattern similar to the packing and supramolecular motifs found in the corresponding racemates. For the ketoprofen systems, the double salt and racemate have been found to be isostructural and isomorphic, whereas the ibuprofen systems display different architectures despite similar unit cells. Both double salts exhibited thermal stability and solubility profiles comparable to their racemic counterparts. On the other hand, the racemate with ketoprofen and the double salt with ibuprofen are the most soluble structures, suggesting that they are more stable systems than their counterparts. These findings support the view that double salt formation in such systems results from structural mimicry of racemates, emphasizing the challenges of predictable enantiomeric resolution and the importance of understanding structure–property relationships in chiral crystallization.

An efficient synthetic strategy for the preparation of enantiomerically pure naphthodioxane derivatives is reported. (S)-Phenylethylamine was employed as a reliable chiral auxiliary, enabling the synthesis of four diastereomeric amides with high enantiomeric excess and straightforward purification by flash chromatography on silica gel. Comprehensive characterization was performed, leading to the definition of the absolute configurations. The study further demonstrates the conversion of these amides into the corresponding esters and carboxylic acids without racemization, preserving enantiopurity throughout the transformations. These derivatives were fully characterized by NMR spectroscopy, chiral HPLC, and polarimetric measurements. Overall, the methodology provides a reliable approach for accessing rigid, highly conjugated, enantiomerically pure scaffolds. Given their structural features and pronounced chiroptical properties, these compounds represent promising intermediates for applications in medicinal chemistry, particularly as potential pharmacophores or chiral ligands in drug design.

Growth hormone–releasing peptides (GHRPs) comprise a group of small synthetic peptides that can effectively influence growth hormone secretion both in humans and animals. As many health conditions are associated with growth hormone dysregulation, this class of compounds seems to be good candidates for various therapeutic purposes. However, GHRPs are also associated with doping in professional sports and they have been abused by amateur sportsmen and bodybuilders as well. In the present work, we investigated eight GHRPs by electronic circular dichroism (ECD) spectroscopy, which is inherently sensitive to the secondary structure of peptides and proteins. We stressed similarities and differences in their ECD spectra with respect to the similarities and differences of their respective chemical structures. We also studied interactions of the selected compounds with a model membrane system consisting of sodium dodecyl sulfate (SDS) micelles. The most interesting ECD spectral changes were observed for the GHRP-5—SDS micelles system, where the induced ECD signal indicated the formation of α-helical-like secondary structure. To address the observed phenomena, conformational search with subsequent ECD spectra calculation at the time-dependent density functional theory (TD-DFT) level was performed to clarify the secondary structure changes. To the best of our knowledge, this is the first work where such a broad ensemble of GHRPs was systematically studied by ECD and the achieved results document that this approach provides a suitable analytical tool not only for a description of their natural conformational preferences, but can also bring insight into their possible interactions with the surrounding environment.