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Investigations have shown that storage bugs seriously harm grains during storage. In the interim, essential oils (EOs) have been proven to be a good botanical pesticide. The anti-Lasioderma serricorne properties of Elsholtzia ciliata essential oil, which was obtained by steam distillation, were evaluated using DL-limonene, carvone, and their two optical isomer components using contact, repelling, and fumigation techniques. Simultaneously, the fumigation, contact, and repellent activities of carvone and its two optical isomers mixed with DL-limonene against L. serruricorne were evaluated. The results showed that E. ciliata, its main components (R-carvone, DL-limonene), and S-carvone exhibited both fumigations (LC50 = 14.47, 4.42, 20.9 and 3.78 mg/L) and contact (LD50 = 7.31, 4.03, 28.62 and 5.63 µg/adult) activity against L.serricorne. A binary mixture (1:1) of R-carvone and DL-limonene displayed an obvious synergistic effect. A binary mixture (1:1) of carvone and its two optical isomers exhibited an obvious synergistic effect, too. Furthermore, the repellent activity of the EO, carvone, and its two optical isomers, DL-limonene, and a combination of them varied. To stop insect damage during storage, E. ciliata and its components can be utilized as bio-insecticides. [ABSTRACT FROM AUTHOR]

An X-ray diffraction study of a transesterification product of N-methyl-N-(trimethoxysilylmethyl)acetamide by 4,5-dibromobenzene-1,2-diol was carried out. It was established that the coordination polyhedron of the silicon atom in an anionic complex is a distorted octahedron disordered due to the superposition of the Δ and Λ optical isomers. The presence of various hydrogen donor groups in bis(cyclohexyl)ammonium cations, solvent ethanol molecules, and non-coordinated 4,5-dibromobenzene-1,2-diol caused the formation of H-bonded chains, while dibromobenzenediol also took part in stacking interactions. [ABSTRACT FROM AUTHOR]

Optical isomers of short peptide Lysine-Tryptophan-Lysine (Lys-{L/D-Trp}-Lys) and Lys-Trp-Lys with an acetate counter-ion were used to study photoinduced intramolecular and intermolecular processes of interest in photobiology. A comparison of L- and D-amino acid reactivity is also the focus of scientists' attention in various specialties because today, the presence of amyloid proteins with D-amino acids in the human brain is considered one of the leading causes of Alzheimer's disease. Since aggregated amyloids, mainly Aβ42, are highly disordered peptides that cannot be studied with traditional NMR and X-ray techniques, it is trending to explore the reasons for differences between L- and D-amino acids using short peptides, as in our article. Using NMR, chemically induced dynamic nuclear polarization (CIDNP) and fluorescence techniques allowed us to detect the influence of tryptophan (Trp) optical configuration on the peptides fluorescence quantum yields, bimolecular quenching rates of Trp excited state, and the photocleavage products formation. Thus, compared with the D-analog, the L-isomer shows a greater Trp excited state quenching efficiency with the electron transfer (ET) mechanism. There are experimental confirmations of the hypothesis about photoinduced ET between Trp and the CONH peptide bond, as well as between Trp and another amide group. [ABSTRACT FROM AUTHOR]

Macrocyclic glycopeptide antibiotics immobilized on silica are one of the effective classes of stationary phases for chiral recognition and HPLC separation of a wide range of optically active compounds. Enantioselectivity primarily depends on the chemical structure of the chiral ligand, immobilization chemistry, and separation conditions. In the present work, three new chiral stationary phases (CSPs) based on macrocyclic antibiotic eremomycin were prepared and investigated for enantioseparation of amino acids. Two eremomycin derivatives, including simple non-substituted amide and bulky adamantyl amide, provided important information on the role of the carboxylic group in the eremomycin structure in the chiral recognition mechanism concerning amino acid optical isomers. One more CSP having a chlorine atom in the same position elucidates the role of the first aromatic ring in the eremomycin structure as a crucial point for chiral recognition. CSP with immobilized chloreremomycin was the most successful among the phases prepared in this work. It was additionally investigated under various separation conditions, including the type and content of the organic solvent in the eluent, the effects of different additives, and the concentration and pH of the buffer. Importantly, an efficient enantioselective separation of amino acids was achieved with pure water as the eluent. [ABSTRACT FROM AUTHOR]

This work is a mini-review highlighting the relevance of the θ metallabis(dicarbollide) [3,3′-Co(1,2-C2B9H11)2]− with its peculiar and differentiating characteristics, among them the capacity to generate hydrogen and dihydrogen bonds, to generate micelles and vesicles, to be able to be dissolved in water or benzene, to have a wide range of redox reversible couples and many more, and to use these properties, in this case, for producing potentiometric membrane sensors to monitor amine-containing drugs or other nitrogen-containing molecules. Sensors have been produced with this monoanionic cluster [3,3′-Co(1,2-C2B9H11)2]−. Other monoanionic boron clusters are also discussed, but they are much fewer. It is noteworthy that most of the electrochemical sensor species incorporate an ammonium cation and that this cation is the species to be detected. Alternatively, the detection of the borate anion itself has also been studied, but with significantly fewer examples. The functions of the borate anion in the membrane are different, even as a doping agent for polypyrrole which was the conductive ground on which the PVC membrane was deposited. Apart from these cases related to closo borates, the bulk of the work has been devoted to sensors in which the θ metallabis (dicarbollide) [3,3′-Co(1,2-C2B9H11)2]− is the key element. The metallabis (dicarbollide) anion, [3,3′-Co(1,2-C2B9H11)2]−, has many applications; one of these is as new material used to prepare an ion-pair complex with bioactive protonable nitrogen containing compounds, [YH]x[3,3′-Co(1,2-C2B9H11)2]y as an active part of PVC membrane potentiometric sensors. The developed electrodes have Nernstian responses for target analytes, i.e., antibiotics, amino acids, neurotransmitters, analgesics, for some decades of concentrations, with a short response time, around 5 s, a good stability of membrane over 45 days, and an optimal selectivity, even for optical isomers, to be used also for real sample analysis and environmental, clinical, pharmaceutical and food analysis. [ABSTRACT FROM AUTHOR]

To develop potent and safer analgesics, we designed and synthesized a novel enantiomerically enriched ethereal analog of (R)-iso-moramide, namely 2-[(2R)-2-(morpholin-4-yl)propoxy]-2,2-diphenyl-1-(pyrrolidin-1-yl)ethan-1-one. The titled active agent can potentially serve as a powerful synthetic opiate with an improved affinity and selectivity toward opioid receptors (ORs). This hypothesis was postulated based on docking studies regarding the respective complexes between the designed ligand and µ-OR, δ-OR, and κ-OR. The key step of the elaborated asymmetric synthesis of novel analog involves lipase-catalyzed kinetic resolution of racemic 1-(morpholin-4-yl)propan-2-ol, which was accomplished on a 10 g scale via an enantioselective transesterification employing vinyl acetate as an irreversible acyl donor in tert-butyl methyl ether (MTBE) as the co-solvent. Next, the obtained homochiral (S)-(+)-morpholino-alcohol (>99% ee) was functionalized into corresponding chloro-derivative using thionyl chloride (SOCl2) or the Appel reaction conditions. Further transformation with N-diphenylacetyl-1-pyrrolidine under phase-transfer catalysis (PTC) conditions using O2-saturated DMSO/NaOH mixture as an oxidant furnished the desired levorotatory isomer of the title product isolated in 26% total yield after three steps, and with 89% ee. The absolute configuration of the key-intermediate of (R)-(–)-iso-moramide was determined using a modified form of Mosher's methodology. The preparation of the optically active dextrorotatory isomer of the titled product (87% ee) was carried out essentially by the same route, utilizing (R)-(–)-1-(morpholin-4-yl)propan-2-ol (98% ee) as a key intermediate. The spectroscopic characterization of the ethereal analog of iso-moramide and the enantioselective retention relationship of its enantiomers using HPLC on the cellulose-based chiral stationary phase were performed. Moreover, as a proof-of-principle, single-crystal X-ray diffraction (XRD) analysis of the synthesized 2-[(2R)-2-(morpholin-4-yl)propoxy]-2,2-diphenyl-1-(pyrrolidin-1-yl)ethan-1-one is reported. [ABSTRACT FROM AUTHOR]

Cell-penetrating peptides (CPPs) have been discovered to deliver chemical drugs, nucleic acids, and macromolecules to permeate cell membranes, creating a novel route for exogenous substances to enter cells. Up until now, various sequence structures and fundamental action mechanisms of CPPs have been established. Among them, arginine-rich peptides with unique cell penetration properties have attracted substantial scientific attention. Due to the positively charged essential amino acids of the arginine-rich peptides, they can interact with negatively charged drug molecules and cell membranes through non-covalent interaction, including electrostatic interactions. Significantly, the sequence design and the penetrating mechanisms are critical. In this brief synopsis, we summarize the transmembrane processes and mechanisms of arginine-rich peptides; and outline the relationship between the function of arginine-rich peptides and the number of arginine residues, arginine optical isomers, primary sequence, secondary and ternary structures, etc. Taking advantage of the penetration ability, biomedical applications of arginine-rich peptides have been refreshed, including drug/RNA delivery systems, biosensors, and blood-brain barrier (BBB) penetration. Understanding the membrane internalization mechanisms and design strategies of CPPs will expand their potential applications in clinical trials. [ABSTRACT FROM AUTHOR]

Organic compounds have been employed in developing new green energy solutions with good cost-efficiency compromise, such as photovoltaics. The light-harvesting process in these applications is a crucial feature that still needs improvements. Here, we studied natural dyes to propose an alternative for enhancing the light-harvesting capability of photovoltaics. We performed density functional theory calculations to investigate the electronic and optical properties of the four natural dyes found in achiote seeds (Bixa orellana L.). Different DFT functionals, and basis sets, were used to calculate the electronic and optical properties of the bixin, norbixin, and their trans-isomers (molecules present in Bixa orellana L.). We observed that the planarity of the molecules and their similar extension for the conjugation pathways provide substantially delocalized wavefunctions of the frontier orbitals and similar values for their energies. Our findings also revealed a strong absorption peak in the blue region and an absorption band over the visible spectrum. These results indicate that Bixa orellana L. molecules can be good candidates for improving light-harvesting in photovoltaics. [ABSTRACT FROM AUTHOR]

The versatile synthesis of (-)-6-desmethyl-fluvirucinine A1 was accomplished at a 24% overall yield through a thirteen-step process from a known vinylpiperidine. The key part involved the elaboration of the distal stereocenters and a macrolactam skeleton via conformationally-induced diastereocontrol and the iterative aza-Claisen rearrangements of lactam precursors. [ABSTRACT FROM AUTHOR]

A stereodivergent total synthesis has been executed based on the plausibly misassigned structure of the unusual marine hydrindane mucosin (1). The topological connectivity of the four contiguous all-carbon stereocenters has been examined by selective permutation on the highlighted core. Thus, capitalizing on an unprecedented stereofacial preference of the cis-fused bicycle[4.3.0]non-3-ene system when a Michael acceptor motif is incorporated, copper-mediated conjugate addition furnished a single diastereomer. Cued by the relative relationship reported for the appendices in the natural product, the resulting anti-adduct was elaborated into a probative target structure 1*. [ABSTRACT FROM AUTHOR]

Ethyl 2,3-diendo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylate ((±)-1) was resolved with O,O'-dibenzoyltartaric acid via diastereomeric salt formation. The efficient synthesis of the enantiomers of 2,3-diendo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylic acid ((+)-7 and (-)-7), 3-endo-aminobicyclo[2.2.2]oct-5-ene-2-exo-carboxylic acid ((+)-5 and (-)-5), cis- and trans-3-aminobicyclo[2.2.2]octane-2-carboxylic acid ((+)-6, (-)-6, (+)-8 and (-)-8) was achieved via isomerization, hydrogenation and hydrolysis of the corresponding esters (-)-1 and (+)-1. The stereochemistry and relative configurations of the synthesized compounds were determined by NMR spectroscopy (based on the 3J(H,H) coupling constants) and X-ray crystallography. [ABSTRACT FROM AUTHOR]

Solvent chirality transfer of (S)-/(R)-limonenes allows the instant generation of optically active PF8P2 aggregates with distinct circular dichroism (CD)/circularly polarized luminescence (CPL) amplitudes with a high quantum yield of 16-20%. The present paper also reports subtle mirror-symmetry-breaking effects in CD-/CPL-amplitude and sign, CD/UV-vis spectral wavelengths, and photodynamics of the aggregates, though the reasons for the anomaly are unsolved. However, these photophysical properties depend on (i) the chemical natures of chiral and achiral molecules when used in solvent quantity, (ii) clockwise and counterclockwise stirring operations, and (iii) the order of addition of limonene and methanol to the chloroform solution. [ABSTRACT FROM AUTHOR]

A reversed-phase gradient liquid chromatographic method has been developed for the quantitative determination of Voriconazole, along with its degradation and diastereomeric impurities in tablet dosage form. Chromatographic separation has been achieved on an Inertsil ODS 3V, 150 × 4.6 mm, 5 μm column. The mobile phase consisting of solvent A 0.05 molar (M) potassium dihydrogen phosphate (pH 2.5 buffer) and solvent B (mi×ture of acetonitrile and methanol in the ratio 90:10 (v/v)), was delivered at a flow rate of 1.2 mL min-1 with the detection wavelength at 256 nm. Resolution of Voriconazole and all five potential impurities was achieved at greater than 2.0 for all pairs of compounds. The drug was subjected to stress conditions such as o×idative, acid and base hydrolysis, and thermal and photolytic degradation. Voriconazole was found to degrade significantly under base hydrolysis stress conditions compared to acid hydrolysis stress conditions. The degradation products were well-resolved from the main peak and its impurities, thus proving the stability-indicating power of the method. The stressed samples were assayed against a reference standard and the mass balance was found to be close to 99.0%. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision, and robustness. [ABSTRACT FROM AUTHOR]

Since the optically active quinuclidin-3-ol is an important intermediate in the preparation of physiologically or pharmacologically active compounds, a new biocatalytic method for the production of chiral quinuclidin-3-ols was examined. Butyrylcholinesterase (BChE; EC 3.1.1.8) was chosen as a biocatalyst in a preparative kinetic resolution of enantiomers. A series of racemic, (R)- and (S)-esters of quinuclidin-3-ol and acetic, benzoic, phthalic and isonicotinic acids were synthesized, as well as their racemic quaternary N-benzyl, meta- and para-N-bromo and N-methylbenzyl derivatives. After the resolution, all N-benzyl protected groups were successfully removed by catalytic transfer hydrogenation with ammonium formate (10% Pd-C). Hydrolyses studies with BChE confirmed that (R)-enantiomers of the prepared esters are much better substrates for the enzyme than (S)-enantiomers. Introduction of bromine atom or methyl group in the meta or para position of the benzyl moiety resulted in a considerable improvement of the stereoselectivity compared to the non-substituted compounds. Optically pure quinuclidin-3-ols were prepared in high yields and enantiopurity by the usage of various N-benzyl protected groups and BChE as a biocatalyst. [ABSTRACT FROM AUTHOR]

Present work employs the QSAR formalism to predict the ED50 anticonvulsant activity of ringed-enaminones, in order to apply these relationships for the prediction of unknown open-chain compounds containing the same types of functional groups in their molecular structure. Two different modeling approaches are applied with the purpose of comparing the consistency of our results: (a) the search of molecular descriptors via multivariable linear regressions; and (b) the calculation of flexible descriptors with the CORAL (CORrelation And Logic) program. Among the results found, we propose some potent candidate open-chain enaminones having ED50 values lower than 10 mg⋅kg-1 for corresponding pharmacological studies. These compounds are classified as Class 1 and Class 2 according to the Anticonvulsant Selection Project. [ABSTRACT FROM AUTHOR]

We report the mechanism and scope of "preferential enrichment", which is an unusual symmetry-breaking enantiomeric resolution phenomenon that is initiated by the solvent-assisted solid-to-solid transformation of a metastable polymorphic form into a thermodynamically stable one during crystallization from the supersaturated solution of certain kinds of racemic mixed crystals (i.e., solid solutions or pseudoracemates) composed of two enantiomers. The mechanism can well be interpreted in terms of a symmetry-breaking complexity phenomenon involving multistage processes that affect each other. [ABSTRACT FROM AUTHOR]

A homogeneous solution of a chiral substance is acquired with an overall asymmetry which is expressed by a specific rotation of a linearly polarized light. Such a solution, despite being at a complete equilibrium, stores configurational entropy in a form of negative entropy which can be nullified by mixing with a solution of the opposite enantiomer. This abundant, yet quite a specific case of inherent negative entropy, resides predominantly in the chiral configuration of the solvent envelopes surrounding the chiral centers. Heat release, amounting to several cal/mol, associated with the annulment of negative entropy in aqueous solutions of D- and L-amino acids, was recently documented by Shinitzky et al. [1]. This heat corresponds almost exclusively to TΔS stored in the solvent envelope upon adoption of a chiral configuration. Simple fundamental expressions which combine configurational entropy and information capacity in chiral solutions have been developed and were found to comply well with the observed heat release upon intermolecular racemization. [ABSTRACT FROM AUTHOR]

The current study evaluates the role of phenylalanine ammonia-lyase (PAL) and the associated metabolic complex in the accumulation of lignin in common wheat plants (Tríticum aestívum L.) at the early stages of ontogenesis. The data analysis was performed using plant samples that had reached Phases 4 and 5 on the Feekes scale—these phases are characterized by a transition to the formation of axial (stem) structures in cereal plants. We have shown that the substrate stimulation of PAL with key substrates, such as L-phenylalanine and L-tyrosine, leads to a significant increase in lignin by an average of 20% in experimental plants compared to control plants. In addition, the presence of these compounds in the nutrient medium led to an increase in the number of gene transcripts associated with lignin synthesis (PAL6, C4H1, 4CL1, C3H1). Inhibition was the main tool of the study. Potential competitive inhibitors of PAL were used: the optical isomer of L-phenylalanine—D-phenylalanine—and the hydroxylamine equivalent of phenylalanine—O-Benzylhydroxylamine. As a result, plants incubated on a medium supplemented with O-Benzylhydroxylamine were characterized by reduced PAL activity (almost one third). The lignin content of the cell wall in plants treated with O-Benzylhydroxylamine was almost halved. In contrast, D-phenylalanine did not lead to significant changes in the lignin-associated metabolic complex, and its effect was similar to that of specific substrates. [ABSTRACT FROM AUTHOR]

(1) Background: Two first-in-class racemic dopamine D1 receptor (D1R) positive allosteric modulator (PAM) chemotypes (1 and 2) were identified from a high-throughput screen. In particular, due to its selectivity for the D1R and reported lack of intrinsic activity, compound 2 shows promise as a starting point toward the development of small molecule allosteric modulators to ameliorate the cognitive deficits associated with some neuropsychiatric disease states; (2) Methods: Herein, we describe the enantioenrichment of optical isomers of 2 using chiral auxiliaries derived from (R)- and (S)-3-hydroxy-4,4-dimethyldihydrofuran-2(3H)-one (d- and l-pantolactone, respectively); (3) Results: We confirm both the racemate and enantiomers of 2 are active and selective for the D1R, but that the respective stereoisomers show a significant difference in their affinity and magnitude of positive allosteric cooperativity with dopamine; (4) Conclusions: These data warrant further investigation of asymmetric syntheses of optically pure analogues of 2 for the development of D1R PAMs with superior allosteric properties. [ABSTRACT FROM AUTHOR]

The study of the L- and D-amino acid properties in proteins and peptides has attracted considerable attention in recent years, as the replacement of even one L-amino acid by its D-analogue due to aging of the body is resulted in a number of pathological conditions, including Alzheimer's and Parkinson's diseases. A recent trend is using short model systems to study the peculiarities of proteins with D-amino acids. In this report, the comparison of the excited states quenching of L- and D-tryptophan (Trp) in a model donor–acceptor dyad with (R)- and (S)-ketoprofen (KP-Trp) was carried out by photochemically induced dynamic nuclear polarization (CIDNP) and fluorescence spectroscopy. Quenching of the Trp excited states, which occurs via two mechanisms: prevailing resonance energy transfer (RET) and electron transfer (ET), indeed demonstrates some peculiarities for all three studied configurations of the dyad: (R,S)-, (S,R)-, and (S,S)-. Thus, the ET efficiency is identical for (S,R)- and (R,S)-enantiomers, while RET differs by 1.6 times. For (S,S)-, the CIDNP coefficient is almost an order of magnitude greater than for (R,S)- and (S,R)-. To understand the source of this difference, hyperpolarization of (S,S)-and (R,S)- has been calculated using theory involving the electron dipole–dipole interaction in the secular equation. [ABSTRACT FROM AUTHOR]

Most pharmaceuticals are stereoisomers that each enantiomer shows dramatically different biological activity. Therefore, the production of optically pure chemicals through sustainable and energy-efficient technology is one of the main objectives in the pharmaceutical industry. Membrane-based separation is a continuous process performed on a large scale that uses far less energy than the conventional thermal separation process. Enantioselective polymer membranes have been developed for chiral resolution of pharmaceuticals; however, it is difficult to generate sufficient enantiomeric excess (ee) with conventional polymers. This article describes a chiral resolution strategy using a composite structure of mixed matrix membrane that employs chiral fillers. We discuss several enantioselective fillers, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), zeolites, porous organic cages (POCs), and their potential use as chiral fillers in mixed matrix membranes. State-of-the-art enantioselective mixed matrix membranes (MMMs) and the future design consideration for highly efficient enantioselective MMMs are discussed. [ABSTRACT FROM AUTHOR]

Herein is reported the synthesis of two Au(III) complexes bearing the (R,R)-(–)-2,3-Bis(tert-butylmethylphosphino)quinoxaline (R,R-QuinoxP*) or (S,S)-(+)-2,3-Bis(tert-butylmethylphosphino)quinoxaline (S,S-QuinoxP*) ligands. By reacting two stoichiometric equivalents of HAuCl4.3H2O to one equivalent of the corresponding QuinoxP* ligand, (R,R)-(–)-2,3-Bis(tert-butylmethylphosphino)quinoxalinedichlorogold(III) tetrachloroaurates(III) (1) and (S,S)-(+)-2,3-Bis(tert-butylmethylphosphino)quinoxalinedichlorogold(III) tetrachloroaurates(III) (2) were formed, respectively, in moderate yields. The structure of (S,S)-(+)-2,3-Bis(tert-butylmethylphosphino)quinoxalinedichlorogold(III) tetrachloroaurates(III) (2) was further confirmed by X-ray crystallography. The antiproliferative activities of the two compounds were evaluated in a panel of cell lines and exhibited promising results comparable to auranofin and cisplatin with IC50 values between 1.08 and 4.83 µM. It is noteworthy that in comparison to other platinum and ruthenium enantiomeric complexes, the two enantiomers (1 and 2) do not exhibit different cytotoxic effects. The compounds exhibited stability in biologically relevant media over 48 h as well as inert reactivity to excess glutathione at 37 °C. These results demonstrate that the Au(III) atom, stabilized by the QuinoxP* ligand, can provide exciting compounds for novel anticancer drugs. These complexes provide a new scaffold to further develop a robust and diverse library of chiral phosphorus Au(III) complexes. [ABSTRACT FROM AUTHOR]

The β-aryl-δ-halo-γ-lactones are known for their antiproliferative activity towards numerous cancer cell lines. The aim of this study was to obtain in the biotransformation process new β-aryl-δ-hydroxy-γ-lactones and compare their activity with the antiproliferative activity of parent compounds. The racemic cis-5-(1-iodoethyl)-4-phenyldihydrofuran-2-one as well as separate enantiomers were transformed in fungal cultures. Among ten tested biocatalysts, three (Absidia cylindrospora AM336, Absidia glauca AM254, and Fusarium culmorum AM10) were able to catalyze the hydrolytic dehalogenation process. The biotransformations processes were highly stereoselective and enantiomerically pure hydroxylactones were obtained (ee ≥ 99%). The iodo- and hydroxylactone enantiomers were subjected to cytotoxic activity evaluation on canine leukemia and lymphoma cell lines. The iodolactones exhibited higher biological potential towards tested cell lines than hydroxylactones. Higher cytotoxic potential was also characteristic for (+)-(4S,5S,6R)-enantiomer of iodolactone compared to its antipode. [ABSTRACT FROM AUTHOR]

Two dimethyl α-hydroxy-arylmethylphosphonates (aryl = Ph and 2-MeOPh) were subjected to optical resolution via diastereomer complex formation applying the acidic calcium salt of O,O′-dibenzoyl-(2R,3R)-tartaric acid as the resolving agent. The dominating diastereomer complexes, whose structure was determined by single crystal X-ray measurements, were obtained in 96% and 68% diastereomer excess values, respectively. After decomposing the diastereomer formations by extraction, and after recrystallizations, the major enantiomer (S and R, respectively) of the α-hydroxyphosphonates were prepared in enantiomeric excess values of 96% and 68%, respectively. The stereostructure of the two α-hydroxy-arylmethylphosphonates was again established by X-ray measurements. Detailed study on the X-ray data allowed valuable conclusions on the nature of the coordination in the complexes (intermolecular interactions), and on the H-bonding. [ABSTRACT FROM AUTHOR]

Astaxanthin from different sources possesses different biological activities and optical isomers. The ingredients of astaxanthin mixtures from different sources on the market have often been mislabeled. Therefore, it is important to determine the sources of astaxanthin and their respective concentrations in a mixture. To solve this problem, a quantitative analysis model was established and further verified. The results showed that the deviation between the calculated concentration and the actual concentration ranged from 0 to 7 µg/mL, and the recovery rate was between 88.90% and 103.56%. This indicates that the quantitative analysis model of astaxanthin was feasible and reliable. This study not only has important applications in the astaxanthin mixture component determination but may also shed light on the quantitative analysis of other sample mixtures with stereoisomers from different sources. [ABSTRACT FROM AUTHOR]

Herbicide safeners selectively protect crops from herbicide injury while maintaining the herbicidal effect on the target weed. To some extent, the detoxification of herbicides is related to the effect of herbicide safeners on the level and activity of herbicide target enzymes. In this work, the expression of the detoxifying enzyme glutathione S-transferase (GST) and antioxidant enzyme activities in maize seedlings were studied in the presence of three potential herbicide safeners: 3-dichloroacetyl oxazolidine and its two optical isomers. Further, the protective effect of chiral herbicide safeners on detoxifying chlorsulfuron in maize was evaluated. All safeners increased the expression levels of herbicide detoxifying enzymes, including GST, catalase (CAT), and peroxidase (POD) to reduce sulfonylurea herbicide phytotoxicity in maize seedlings. Our results indicate that the R-isomer of 3-(dichloroacetyl)-2,2,5-trimethyl-1,3-oxazolidine can induce glutathione (GSH) production, GST activity, and the ability of GST to react with the substrate 1-chloro-2,4-dinitrobenzene (CDNB) in maize, meaning that the R-isomer can protect maize from damage by chlorsulfuron. Information about antioxidative enzyme activity was obtained to determine the role of chiral safeners in overcoming the oxidative stress in maize attributed to herbicides. The interaction of safeners and active target sites of acetolactate synthase (ALS) was demonstrated by molecular docking modeling, which indicated that both isomers could form a good interaction with ALS. Our findings suggest that the detoxification mechanism of chiral safeners might involve the induction of the activity of herbicide detoxifying enzymes as well as the completion of the target active site between the safener and chlorsulfuron. [ABSTRACT FROM AUTHOR]

Organic compounds are present as complex mixtures in extraterrestrial materials including meteorites, which may have played important roles in the origin of life on the primitive Earth. However, the distribution and formation mechanisms of meteoritic organic compounds are not well understood, because conventional analytical methods have limited resolution and sensitivity to resolve their molecular complexity. In this study, advanced instrumental development and analyses are proposed in order to study the trace organic compounds of extraterrestrial materials: (1) a clean room environment to avoid organic contamination during analysis; (2) high-mass-resolution analysis (up to ~150,000 m/Δm) coupled with high-performance liquid chromatography (HPLC) in order to determine the elemental composition using exact mass for inferring the chemical structure; (3) superior chromatographic separation using a two-dimensional system in order to determine the structural and optical isomers of amino acids; and (4) in situ organic compound analysis and molecular imaging of the sample surface. This approach revealed a higher complexity of organic compounds with a heterogeneous distribution in meteorites. These new methods can be applied to study the chemical evolution of meteoritic organic compounds as well as the molecular occurrence in very-low-mass extraterrestrial materials such as asteroid-returned samples. [ABSTRACT FROM AUTHOR]