53,905 results match your criteria chiral


Phaeosphspirone (1/1'), a pair of unique polyketide enantiomers with an unusual 6/5/5/6 tetracyclic ring from the desert plant endophytic fungus Phaeosphaeriaceae sp.

Phytochemistry 2021 Nov 30;194:112969. Epub 2021 Nov 30.

Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicines, Ministry of Education, Institute of Medicinal Plant Development, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, 100193, People's Republic of China. Electronic address:

Phaeosphspirone, an undescribed polyketide with a unique 6/5/5/6-fused tetracyclic system, and two known analogues, herbarin and O-methylherbarin, were purified from the endophytic fungus Phaeosphaeriaceae sp. isolated from the desert plant Bassia dasyphylla. The connectivity and relative configuration of phaeosphspirone was elucidated by comprehensive HR-ESI-MS and NMR analysis together with a computer-assisted structure elucidation (CASE) method. Read More

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November 2021

Chiral fungicide penconazole: Absolute configuration, bioactivity, toxicity, and stereoselective degradation in apples.

Sci Total Environ 2021 Nov 30:152061. Epub 2021 Nov 30.

Institute of Pomology, Chinese Academy of Agricultural Sciences/Laboratory of Quality & Safety Risk Assessment for Fruit (Xingcheng), Ministry of Agriculture and Rural Affairs, Xingcheng 125100, China; Center for Modern Agricultural Development Service, 033000, China.

Traditional evaluation of chiral pesticides can lead to inaccurate results, as their enantiomers may show different properties. Penconazole, a chiral triazole fungicide with two enantiomers, is widely applied to protect against phytopathogens. In this study, its absolute configuration, bioactivity, ecotoxicity, and stereoselective degradation were investigated at the enantiomeric level in detail. Read More

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November 2021

Local Growth Mediated by Plasmonic Hot Carriers: Chirality from Achiral Nanocrystals Using Circularly Polarized Light.

Nano Lett 2021 Dec 3. Epub 2021 Dec 3.

Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China.

Plasmonic nanocrystals and their assemblies are excellent tools to create functional systems, including systems with strong chiral optical responses. Here we study the possibility of growing chiral plasmonic nanocrystals from strictly nonchiral seeds of different types by using circularly polarized light as the chirality-inducing mechanism. We present a novel theoretical methodology that simulates realistic nonlinear and inhomogeneous photogrowth processes in plasmonic nanocrystals, mediated by the excitation of hot carriers that can drive surface chemistry. Read More

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December 2021

Merging Supramolecular and Covalent Helical Polymers: Four Helices Within a Single Scaffold.

J Am Chem Soc 2021 Dec 3. Epub 2021 Dec 3.

Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain.

Supramolecular and covalent polymers share multiple structural effects such as chiral amplification, helical inversion, sergeants and soldiers, or majority rules, among others. These features are related to the axial helical structure found in both types of materials, which are responsible for their properties. Herein a novel material combining information and characteristics from both fields of helical polymers, supramolecular (oligo(-phenyleneethynylene) (OPE)) and covalent (poly(acetylene) (PA)), is presented. Read More

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December 2021

Catalytic Asymmetric Hydroalkoxylation of C-C Multiple Bonds.

Chem Rev 2021 Dec 3. Epub 2021 Dec 3.

Max-Planck-Institut für Kohlenforschung, Kaiser Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.

Asymmetric hydroalkoxylation of alkenes constitutes a redox-neutral and 100% atom-economical strategy toward enantioenriched oxygenated building blocks from readily available starting materials. Despite their great potential, catalytic enantioselective additions of alcohols across a C-C multiple bond are particularly underdeveloped, especially compared to other hydrofunctionalization methods such as hydroamination. However, driven by some recent innovations, e. Read More

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December 2021

Analysis of Charge Order in the Kagome Metal AV_{3}Sb_{5} (A=K,Rb,Cs).

Phys Rev Lett 2021 Nov;127(21):217601

Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.

Motivated by the recent discovery of unconventional charge order, we develop a theory of electronically mediated charge density wave formation in the family of kagome metals AV_{3}Sb_{5} (A=K,Rb,Cs). The intertwining of van Hove filling and sublattice interference suggests a three-fold charge density wave instability at T_{CDW}. From there, the charge order forming below T_{CDW} can unfold into a variety of phases capable of exhibiting orbital currents and nematicity. Read More

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November 2021

Superstring Loop Amplitudes from the Field Theory Limit.

Phys Rev Lett 2021 Nov;127(21):211603

Centre for Research in String Theory, School of Physics and Astronomy, Queen Mary University of London, E1 4NS, London, United Kingdom.

We propose a procedure to determine the moduli-space integrands of loop-level superstring amplitudes for massless external states in terms of the field theory limit. We focus on the type II superstring. The procedure is to (i) take a supergravity loop integrand written in a BCJ double-copy representation, (ii) use the loop-level scattering equations to translate that integrand into the ambitwistor string moduli-space integrand, localised on the nodal Riemann sphere, and (iii) uplift that formula to one on the higher-genus surface valid for the superstring, guided by modular invariance. Read More

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November 2021

Ni/Chiral Sodium Carboxylate Dual Catalyzed Asymmetric O-Propargylation.

J Am Chem Soc 2021 Dec 3. Epub 2021 Dec 3.

Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry, University of Science and Technology of China, Hefei 230026, China.

A highly enantioselective O-propargylation catalyzed by combining a phosphine-nickel complex and an axially chiral sodium dicarboxylate has been developed. The transformation features mild reaction conditions, a broad substrate scope, and excellent functional group tolerance, offering an efficient approach to an array of enantioenriched -propargyl hydroxylamines. Mechanistic studies support the presumed role of the chiral carboxylate as a counterion for nickel catalysis enabling the discovery of highly stereoselective transformations. Read More

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December 2021

Chirality-Puckering correlation and intermolecular interactions in Sphingosines: Rotational spectroscopy of jaspine B3 and its monohydrate.

Spectrochim Acta A Mol Biomol Spectrosc 2021 Nov 16:120531. Epub 2021 Nov 16.

Departamento de Química Física y Química Inorgánica, Facultad de Ciencias - I.U. CINQUIMA, Universidad de Valladolid, Paseo de Belén 7, Valladolid 47011, Spain.

Chirality is determinant for sphingosine biofunctions and pharmacological activity, yet the reasons for the biological chiral selection are not well understood. Here, we characterized the intra- and intermolecular interactions at the headgroup of the cytotoxic anhydrophytosphingosine jaspine B, revealing chirality-dependent correlations between the puckering of the ring core and the formation of amino-alcohol hydrogen bond networks, both in the monomer and the monohydrate. Following the specific synthesis of a shortened 3-carbon side-chain molecule, denoted jaspine B3, six different isomers were observed in a jet expansion using broadband (chirped-pulsed) rotational spectroscopy. Read More

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November 2021

Gene mining, codon optimization and analysis of binding mechanism of an aldo-keto reductase with high activity, better substrate specificity and excellent solvent tolerance.

PLoS One 2021 2;16(12):e0260787. Epub 2021 Dec 2.

College of Chemical Engineering, Huaqiao University, Xiamen, China.

The biosynthesis of chiral alcohols has important value and high attention. Aldo-keto reductases (AKRs) mediated reduction of prochiral carbonyl compounds is an interesting way of synthesizing single enantiomers of chiral alcohols due to the high enantio-, chemo- and regioselectivity of the enzymes. However, relatively little research has been done on characterization and apply of AKRs to asymmetric synthesis of chiral alcohols. Read More

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December 2021

Chiral Phosphoric Acid Catalyzed Desymmetrization of Cyclopentendiones via Friedel-Crafts Conjugate Addition of Indolizines.

Org Lett 2021 Dec 2. Epub 2021 Dec 2.

Key Laboratory of Functionalized Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecule-Based Materials (State Key Laboratory Cultivation Base), College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241002, Anhui, P. R. China.

An organocatalytic highly diastero- and enantioselective Friedel-Crafts conjugate addition of indolizines to prochiral cyclopentenediones has been successfully developed. This desymmetric transformation provides a direct access to the desired indolizine-substituted cyclopentanediones in yields of 62-91% and excellent stereoselectivities. The utility of the approach was demonstrated by diverse late-stage functionalizations through reduction or oxidation. Read More

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December 2021

Full-Color Tunable Circularly Polarized Luminescence Induced by the Crystal Defect from the Co-assembly of Chiral Silver(I) Clusters and Dyes.

J Am Chem Soc 2021 Dec 2. Epub 2021 Dec 2.

Henan Key Laboratory of Crystalline Molecular Functional Materials, Henan International Joint Laboratory of Tumor Theranostical Cluster Materials, Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou 450001, China.

Four pairs of defective crystals exhibiting full-color emission and circularly polarized luminescence (CPL) with high luminescence dissymmetry factor () values (∼3 × 10) were successfully obtained by doping dye molecules into the chiral crystalline metal cluster-based matrixes. The dye molecules function as defect inducers and confer fluorescence on the crystals. Studies reveal that electrostatic interactions provide the main impetus in generating defective crystals, and the restricted effect of chiral space and the weak interactions in defect crystal enable the efficient chiral transfer from the intrinsically chiral host silver(I) clusters to achiral luminescent dopants and finally induce them to emit bright CPL. Read More

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December 2021

Ultraviolet Light Detectable Circularly Polarized Room Temperature Phosphorescence in Chiral Naphthalimide Self-Assemblies.

ACS Nano 2021 Dec 2. Epub 2021 Dec 2.

School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People's Republic of China.

The combination of circularly polarized luminescence (CPL) and pure-organic room temperature phosphorescence (RTP) potentially facilitates the construction of organic chiroptical optoelectronics and display materials, which however are challenging to use in realizing smart control of luminescent colors and switchable chiroptical properties. Here, we show a host-guest strategy to fabricate color-tunable RTP-based circularly polarized phosphorescence. Napthalimides were conjugated directly to chiral segments, of which supramolecular chirality and CPL activities in solid-states could be triggered by substituting bromine atoms on amines. Read More

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December 2021

Catalytic asymmetric synthesis of α-stereogenic carboxylic acids: recent advances.

Org Biomol Chem 2021 Dec 2. Epub 2021 Dec 2.

Shaanxi Key Laboratory of Chemical Reaction Engineering, College of Chemistry and Chemical Engineering, Yan'an University, Yan'an 716000, China.

Chiral carboxylic acids bearing an α-stereogenic center constitute the backbone of many natural products and therapeutic reagents as well as privileged chiral ligands and catalysts. Hence, it is not surprising that a large number of elegant catalytic asymmetric strategies have been developed toward the efficient synthesis of α-chiral carboxylic acids, such as α-hydroxy acids and α-amino acids. In this review, the recent advances in asymmetric synthesis of α-stereogenic free carboxylic acids organocatalysis and transition metal catalysis are summarized (mainly from 2010 to 2020). Read More

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December 2021

Remote Amino Acid Recognition Enables Effective Hydrogen Peroxide Activation at a Manganese Oxidation Catalys.

Angew Chem Int Ed Engl 2021 Dec 1. Epub 2021 Dec 1.

Universitat de Girona, Institut de Química Computacional i Catàlisi, SPAIN.

Precise delivery of a proton plays a key role in O 2 activation at iron oxygenases, enabling the crucial O-O cleavage step that generates the oxidizing high valent metal-oxo species. Such proton is delivered by acidic residues that may either directly bind the iron center or lie in its second coordination sphere. Herein, a supramolecular strategy for enzyme-like H 2 O 2 activation at a biologically inspired manganese catalyst, with nearly stoichiometric amount (1-1. Read More

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December 2021

Transformation of Crowded Oligoarylene into Perylene-Cored Chiral Nanographene by Sequential Oxidative Cyclization and 1,2-Phenyl Migration.

Angew Chem Int Ed Engl 2021 Dec 2. Epub 2021 Dec 2.

Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, 800 Dongchuan Road, 200240, Shanghai, CHINA.

Synthetic innovation to construct sophisticated nanographenes is of fundamental significance for a variety of advanced applications. Herein, we report a distinctive method to prepare π -extended chiral nanographenes with 29 benzenoid rings and two helical breaches from a highly crowded perylene-cored oligoarylene precursor. Under Scholl's condition, the reaction majorly involves the regioselective and sequential cyclization in the peri - and bay regions of the perylene core, and the complanation of the 1-phenyl[5]helicene intermediate module via 1,2-phenyl migration. Read More

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December 2021

Redox deracemization of phosphonate-substituted dihydropyrimidines.

Org Biomol Chem 2021 Dec 2. Epub 2021 Dec 2.

School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.

An efficient redox deracemization of the phosphonic ester substituted 3,4-dihydropyrimidin-2-one (DHPM) derivatives is described. The one-pot deracemization strategy consisted of the oxidization to destroy the stereocenter center and the following asymmetric transfer hydrogenation to regenerate the chiral carbon center with the vicinal phosphonic ester group, providing a series of optically active phosphonate substituted DHPMs with up to 96% ee. Read More

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December 2021

Robustness of the chiral-icosahedral golden shell I-Au in multi-shell structures.

J Chem Phys 2021 Nov;155(20):204307

Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0697, USA.

Motivated by the recent theoretical discovery [S.-M. Mullins et al. Read More

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November 2021

Interconversion-controlled liquid-liquid phase separation in a molecular chiral model.

J Chem Phys 2021 Nov;155(20):204502

Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA.

Liquid-liquid phase separation of fluids exhibiting interconversion between alternative states has been proposed as an underlying mechanism for fluid polyamorphism and may be of relevance to the protein function and intracellular organization. However, molecular-level insight into the interplay between competing forces that can drive or restrict phase separation in interconverting fluids remains elusive. Here, we utilize an off-lattice model of enantiomers with tunable chiral interconversion and interaction properties to elucidate the physics underlying the stabilization and tunability of phase separation in fluids with interconverting states. Read More

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November 2021

Dual-Mode Circularly Polarized Light Emission and Metal-Enhanced Fluorescence Realized by the Luminophore-Chiral Cellulose Nanocrystal Interfaces.

ACS Appl Mater Interfaces 2021 Dec 1. Epub 2021 Dec 1.

State Key Laboratory of Metal Matrix Composites, School of Material Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.

Circularly polarized (CP) light has attracted wide attention for its great potential in broad applications. However, it remains a challenge to generate left-handed and right-handed circularly polarized (LCP and RCP) light from cellulose nanocrystal (CNC)-based materials only with an intrinsic left-handed chiral structure, owing to the pattern of CP light emission primarily based on the chirality of materials. Herein, a separation structure of luminophore layers and chiral CNCs was provided to achieve dual-mode CP light emission by building a luminophore-chiral CNC interface. Read More

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December 2021

Probing Catalyst Function - Electronic Modulation of Chiral Polyborate Anionic Catalysts.

J Org Chem 2021 Dec 2. Epub 2021 Dec 2.

Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.

Boroxinate complexes of VAPOL and VANOL are a chiral anionic platform that can serve as a versatile staging arena for asymmetric catalysis. The structural underpinning of the platform is a chiral polyborate core that covalently links together alcohols (or phenols) and vaulted biaryl ligands. The polyborate platform is assembled in situ by the substrate of the reaction, and thus a multiplex of chiral catalysts can be rapidly assembled from various alcohols (or phenols) and bis-phenol ligands for screening of catalyst activity. Read More

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December 2021

Interparticle Gap Geometry Effects on Chiroptical Properties of Plasmonic Nanoparticle Assemblies.

Nanotechnology 2021 Dec 1. Epub 2021 Dec 1.

University of Waterloo, 200 University Ave W, Waterloo, Ontario, N2L 3G1, CANADA.

Chiral linear assemblies of plasmonic nanoparticles with chiral optical activity often show low asymmetry factors. Systematic understanding of the structure-property relationship in these systems must be improved to facilitate rational design of their chiroptical response. Here we study the effect of large-area interparticle gaps in chiral linear nanoparticle assemblies on their chiroptical properties using a tetrahelix structure formed by a linear face-to-face assembly of nanoscale Au tetrahedra. Read More

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December 2021

Artificial Biomolecular Channels: Enantioselective Transmembrane Transport of Amino Acids Mediated by Homochiral Zirconium Metal-Organic Cages.

J Am Chem Soc 2021 Dec 1. Epub 2021 Dec 1.

School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China.

Natural transport channels (or carriers), such as aquaporins, are a distinct type of biomacromolecule capable of highly effective transmembrane transport of water or ions. Such behavior is routine for biology but has proved difficult to achieve in synthetic systems. Perhaps most significantly, the enantioselective transmembrane transport of biomolecules is an especially challenging problem both for chemists and for natural systems. Read More

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December 2021

Rods in a lyotropic chromonic liquid crystal: emergence of chirality, symmetry-breaking alignment, and caged angular diffusion.

Soft Matter 2021 Dec 1. Epub 2021 Dec 1.

Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, 19104, USA.

In lyotropic chromonic liquid crystals (LCLCs), twist distortion of the nematic director costs much less energy than splay or bend distortion. This feature leads to novel mirror-symmetry breaking director configurations when the LCLCs are confined by interfaces or contain suspended particles. Spherical colloids in an aligned LCLC nematic phase, for example, induce chiral director perturbations ("twisted tails"). Read More

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December 2021

Palladium-Catalyzed Asymmetric Cross-Coupling Reactions of Cyclobutanols and Unactivated Olefins.

Org Lett 2021 Dec 1. Epub 2021 Dec 1.

Department of Chemistry, Fudan University, 2005 Songhu Road, Shanghai 200438, P. R. China.

Transition-metal-catalyzed activations of carbon-carbons bonds of small strained rings have widespread applications in synthetic and medicinal chemistry. However, coupling reactions of cyclobutanols involving β-carbon elimination to construct C(sp)-C(sp) bonds have scarcely been developed. Here, we demonstrate a highly enantioselective Pd-catalyzed intermolecular C(sp)-C(sp) coupling reaction of a broad range of cyclobutanol derivatives and unactivated alkenes, allowing convenient access to a series of chiral benzene-fused cyclic compounds in a highly regio-, chemo-, and enantioselective manner. Read More

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December 2021

Enantioselective Construction of Chiral Bispiro[Oxindole-Pyrrolidine-Pyrazolone] Derivatives via Sequential and One-Pot Mannich/Hydroamination Reaction.

J Org Chem 2021 Dec 1. Epub 2021 Dec 1.

Department of Organic Chemistry, Charles University, Hlavova 8, 12843 Prague, Czech Republic.

The atom-economic method for the preparation of novel bispirocyclic compounds containing three fused heterocyclic scaffolds privileged in drug discovery was developed by using a chiral amine-squaramide Mannich reaction and Au(I)-catalyzed hydroamination. The developed synthetic strategy performed either stepwise or as a one-pot process allows the formation of chiral bispirocyclic [oxindole-pyrrolidine-pyrazolones] in high yields (up to 75%) with excellent enantioselectivities (up to 99%). Read More

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December 2021

Ultrasensitive Electrochemical Impedance Chiral Discrimination and Sensing of Tryptophan Isomers Based on Core-Shell-Structured Au-Ag Nanoparticles.

Langmuir 2021 Dec 1. Epub 2021 Dec 1.

Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China.

Au-Ag nanoparticles (Au-Ag NPs) with a core-shell structure are prepared and used for ultrasensitive electrochemical impedance (EI) discrimination of the isomers of tryptophan (Trp). As revealed by circular dichroism, rotary polarization caused by the Au-Ag NPs is consistent with D-Trp but opposite to L-Trp, and thus, the Au-Ag NPs can selectively combine with D-Trp through preferential interactions. Compared with Au-Ag NPs, the composites of D-Trp and Au-Ag NPs (Au-Ag NPs/D-Trp) display significantly increased charge transfer resistance (); differently, the of Au-Ag NPs/L-Trp remains almost unchanged because the Au-Ag NPs exhibit poor affinity toward L-Trp. Read More

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December 2021

Amplifying inorganic chirality using liquid crystals.

Nanoscale 2021 Dec 1. Epub 2021 Dec 1.

Division of Nanomaterials & Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China.

Chiral inorganic nanostructures have drawn extensive attention thanks to their unique physical properties as well as multidisciplinary applications. Amplifying inorganic chirality using liquid crystals (LCs) is an efficient way to enhance the parented inorganic asymmetry owing to chirality transfer. Herein, the universal synthetic methods and structural characterizations of chiral inorganic-doped LC hybrids are introduced. Read More

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December 2021

The Effects of Benoxacor on the Liver and Gut Microbiome of C57BL/6 Mice.

Toxicol Sci 2021 Nov 29. Epub 2021 Nov 29.

Department of Occupational and Environmental Health, The University of Iowa, Iowa City, Iowa 52242, United States.

The toxicity of many "inert" ingredients of pesticide formulations, such as safeners, is poorly characterized, despite evidence that humans may be exposed to these chemicals. Analysis of ToxCast data for dichloroacetamide safeners with the ToxPi tool identified benoxacor as the safener with the highest potential for toxicity, especially liver toxicity. Benoxacor was subsequently administered to mice via oral gavage for three days at concentrations of 0, 0. Read More

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November 2021

Enantioselective separation, analysis and stereoselective dissipation of the chiral pesticide cloquintocet-mexyl using a modified QuEChERS method by high-performance liquid chromatography tandem mass spectrometry.

Chemosphere 2021 Nov 27:133084. Epub 2021 Nov 27.

School of Pharmacy, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang, 110016, Liaoning Province, People's Republic of China. Electronic address:

An efficient and novel enantioseparation method was successfully developed and validated to quantify the enantiomers of cloquintocet-mexyl in soil, millet, enoki mushroom, oilseed rape, and watermelon using a modified QuEChERS technique combined with HPLC-MS/MS. This method showed reliable performances for determining both enantiomers of cloquintocet-mexyl in all five matrices. The limits of detection and limits of quantification were in the range of 0. Read More

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November 2021