1,149 results match your criteria racemic mixtures

Radiosynthesis and Evaluation of Talazoparib and Its Derivatives as PARP-1-Targeting Agents.

Biomedicines 2021 May 18;9(5). Epub 2021 May 18.

Department of Radiology, School of Medicine, Washington University in Saint Louis, Saint Louis, MO 63110, USA.

Poly (ADP-ribose) polymerase-1 (PARP-1) is a critical enzyme in the DNA repair process and the target of several FDA-approved inhibitors. Several of these inhibitors have been radiolabeled for non-invasive imaging of PARP-1 expression or targeted radiotherapy of PARP-1 expressing tumors. In particular, derivatives of olaparib and rucaparib, which have reduced trapping potency by PARP-1 compared to talazoparib, have been radiolabeled for these purposes. Read More

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Peptoids as a Chiral Stationary Phase for Liquid Chromatography: Insights from Molecular Dynamics Simulations.

Biomacromolecules 2021 Jun 19;22(6):2573-2581. Epub 2021 May 19.

Department of Industrial Chemistry ≪ Toso Montanari ≫, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy.

Peptoids are peptide regioisomers with attractive structural tunability in terms of sequence and three-dimensional arrangement. Peptoids are foreseen to have a great potential for many diverse applications, including their utilization as a chiral stationary phase in chromatography. To achieve chiral recognition, a chiral side chain is required to allow specific interactions with a given enantiomer from a racemic mixture. Read More

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Enantioselective and Synergistic Herbicidal Activities of Common Amino Acids Against and .

Molecules 2021 Apr 4;26(7). Epub 2021 Apr 4.

Department of Chemistry, School of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand.

Amino acids have a wide range of biological activities, which usually rely on the stereoisomer presented. In this study, glycine and 21 common α-amino acids were investigated for their herbicidal property against Chinese amaranth ( L.) and barnyard grass ( (L. Read More

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Chirality Remote Control in Nanoporous Materials by Circularly Polarized Light.

J Am Chem Soc 2021 May 29;143(18):7059-7068. Epub 2021 Apr 29.

Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.

The ability to dynamically control chirality remains a grand challenge in chemistry. Although many molecules possess chiral isomers, lacking their isolation, for instance during photoisomerization, results in racemic mixtures with suppressed enantiospecific chiral properties. Here, we present a nanoporous solid in which chirality and enantioselective enrichment is induced by circularly polarized light (CPL). Read More

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Defining the Landscape of the Pauling-Corey Rippled Sheet: An Orphaned Motif Finding New Homes.

Acc Chem Res 2021 05 26;54(10):2488-2501. Epub 2021 Apr 26.

Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States.

When peptides are mixed with their mirror images in an equimolar ratio, two-dimensional periodic structural folds can form, in which extended peptide strands are arrayed with alternating chirality. The resultant topography class, termed the rippled β-sheet, was introduced as a theoretical concept by Pauling and Corey in 1953. Unlike other fundamental protein structural motifs identified around that time, including the α-helix and the pleated β-sheet, it took several decades before conclusive experimental data supporting the proposed rippled β-sheet motif were gained. Read More

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Vibrational circular dichroism studies of exceptionally strong chirality inducers in liquid crystals.

Phys Chem Chem Phys 2021 Apr;23(16):10021-10028

Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.

7,7'-Disubstituted 2,2'-methylenedioxy-1,1'-binaphthyls are highly efficient chirality inducers in nematic liquid crystals. The absolute configuration of these compounds is, however, hard to determine as they only crystallize as racemic mixtures. In this work a Vibrational Circular Dichroism (VCD) study is reported that provides an unambiguous determination of the absolute configuration of these compounds. Read More

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Phosphonates enantiomers receiving with fungal enzymatic systems.

Microb Cell Fact 2021 Apr 7;20(1):81. Epub 2021 Apr 7.

Department of Biochemistry, Molecular Biology and Biotechnology, Laboratory of Biotechnology, Wrocław University of Science and Technology, Wrocław, Poland.

Background: Phosphonates derivatives are in the area of interests because of their unique chemical-physical features. These compounds manifest variety of biological interactions within the sensitive living cells, including impact on particular enzymes activities. Biological "cause and effect" interactions are based upon the specific matching between the structures and/or compounds and this is usually the result of proper optical configurations of particular chiral moieties. Read More

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Automated chiral method screening - Evaluation of generated chromatographic data sets to further optimize screening efficiency.

J Chromatogr A 2021 May 23;1644:462094. Epub 2021 Mar 23.

NIBR Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Novartis Pharma AG, Novartis Campus, 4002 Basel (Switzerland).

We set up an automated screening process to routinely test 10 chiral supercritical fluid chromatography (SFC) methods - five columns combined with two co-solvents - as part of a chiral separation lab workflow. Proprietary software tools enabled automated method screening of racemates, parallel evaluation of the resulting chromatograms for enantiomer separation and report generation. This process is largely automated and resulted in an efficient and reliable lab process with a minimum requirement for human intervention. Read More

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Enantio- and Regioconvergent Nickel-Catalyzed C(sp )-C(sp ) Cross-Coupling of Allylic Electrophiles Steered by a Silyl Group.

Angew Chem Int Ed Engl 2021 Jun 5;60(24):13652-13655. Epub 2021 May 5.

Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany.

A two-step sequence for the enantio- and diastereoselective synthesis of exclusively alkyl-substituted acyclic allylic systems with a stereocenter in the allylic position is reported. The asymmetric induction and the site selectivity are controlled in an enantio- and regioconvergent nickel-catalyzed C(sp )-C(sp ) cross-coupling of regioisomeric mixtures of racemic α-/γ-silylated allylic halides and primary alkylzinc reagents. The silyl group steers the allylic displacement towards the formation of the vinylsilane regioisomer, and the resulting C(sp )-Si bond serves as a linchpin for the installation of various C(sp ) substituents in a subsequent step. Read More

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Meroterpenoids from the leaves of Psidium guajava (guava) cultivated in Korea using MS/MS-based molecular networking.

Phytochemistry 2021 Jun 31;186:112723. Epub 2021 Mar 31.

Korea Bioactive Natural Material Bank, Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, 151-742, Republic of Korea. Electronic address:

MS/MS-based molecular networking showed differences in the chemical profiles, especially the terpenoid-coupled-phloroglucinol clusters, of Psidium guajava grown in Jeju Island of South Korea ("Jejuguava"), Vietnam and China. A chemical investigation of the 95% EtOH extract of Jejuguava leaves revealed meroterpenoids characterized by a dihydropyran ring junction between an acylphloroglucinol structure and terpenoid, and named jejuguajavones A-J (1-10). Compounds (±)-8-(±)-10 are racemic mixtures that were separated using a chiral HPLC column. Read More

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Pyrrolyl 4-quinolone alkaloids from the mangrove endophytic fungus Penicillium steckii SCSIO 41025: Chiral resolution, configurational assignment, and enzyme inhibitory activities.

Phytochemistry 2021 Jun 16;186:112730. Epub 2021 Mar 16.

CAS Key Laboratory of Tropical Marine Bio-resources and Ecology/Guangdong Key Laboratory of Marine Materia Medica, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, PR China; Institute of Marine Drugs, Guangxi University of Chinese Medicine, Nanning, 530200, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China. Electronic address:

Six undescribed 4-quinolone alkaloids, including four racemic mixtures, (±)-oxypenicinolines A-D, and two related ones, penicinolines F and G, together with seven known analogues, were isolated from the mangrove-derived fungus Penicillium steckii SCSIO 41025 (Trichocomaceae). The racemates were separated by HPLC using chiral columns. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis, electronic circular dichroism (ECD) experiments, and single-crystal X-ray diffraction analysis. Read More

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The enantiomer-selective metabolism of hexabromocyclododecanes (HBCDs) by human HepG2 cells.

Sci Total Environ 2021 May 4;768:144430. Epub 2021 Jan 4.

School of Agriculture, Sun Yat-sen University, Guangzhou 510275, China. Electronic address:

Although hepatic metabolism of hexabromocyclododecanes (HBCDs) played critical roles in the selective bioaccumulation of HBCDs in humans, the hepatic metabolism patterns of its enantiomers remained ambiguous. Aiming to elucidate the mechanism on hepatic metabolism of hexabromocyclododecanes (HBCDs) enantiomers, the enantiomers ((+)-α-HBCD, (-)-α-HBCD, (+)-γ-HBCD, and (-)-γ-HBCD), the diastereoisomers (α-, β-, and γ-HBCDs) and the mixed of α- and γ-HBCDs were incubated with human HepG2 cell under different exposure levels in the present study. The clearance percentages ranked as γ-HBCD enantiomers >β-HBCD enantiomers >α-HBCD enantiomers at the same exposure levels. Read More

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Further prenylated anthranoids from Harungana madagascariensis.

Phytochemistry 2021 Jun 9;186:112711. Epub 2021 Mar 9.

Department of TCMs Pharmaceuticals and State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, People's Republic of China. Electronic address:

Ten undescribed anthranoids, including three anthraquinone acetals as racemic mixtures, (±)-kenganthranol G-I, and seven prenylated anthranols, (±)-kenganthranol J-M and harunganol G-I, together with thirteen known compounds, were isolated from the stem bark of Harungana madagascariensis. The structures of (±)-kenganthranol G and (±)-kenganthranol J were confirmed by X-ray crystallography. (±)-Kenganthranol G was separated into (+)-kenganthranol G and (-)-kenganthranol G by chiral HPLC and their absolute configurations were established by electronic circular dichroism. Read More

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Bright Long-Lived Circularly Polarized Luminescence in Chiral Chromium(III) Complexes.

Angew Chem Int Ed Engl 2021 04 11;60(18):10095-10102. Epub 2021 Mar 11.

Department of Inorganic and Analytical Chemistry, University of Geneva, quai E. Ansermet 30, 1211, Geneva 4, Switzerland.

A series of highly emissive inert and chiral Cr complexes displaying dual circularly polarized luminescence (CPL) within the NIR region have been prepared and characterized. The helical [Cr(dqpR) ] (dqp=2,6-di(quinolin-8-yl)pyridine; R=OCH , Br or C≡CH) complexes were synthesized as racemic mixtures and resolved into their respective PP and MM enantiomers by chiral stationary phase HPLC. The corresponding enantiomers show large g ≈0. Read More

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3-aryl-indolinones derivatives as antiplasmodial agents: synthesis, biological activity and computational analysis.

Nat Prod Res 2021 Mar 11:1-7. Epub 2021 Mar 11.

Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.

Malaria is an infectious illness, affecting vulnerable populations in Third World countries. Inspired by natural products, indole alkaloids have been used as a nucleus to design new antimalarial drugs. So, eighteen oxindole derivatives, analogues were obtained with moderate to excellent yields. Read More

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Conversion of Racemic Unnatural Amino Acids to Optically Pure Forms by a Coupled Enzymatic Reaction.

Molecules 2021 Feb 26;26(5). Epub 2021 Feb 26.

Department of Chemistry, Sogang University, 35 Baekbeomro Mapogu, Seoul 121-742, Korea.

Genetic code expansion (GCE) technology is a useful tool for the site-specific modification of proteins. An unnatural amino acid (UAA) is one of the essential components of this technique, typically required at high concentration (1 mM or higher) in growth medium. The supply of UAAs is an important limitation to the application of GCE technology, as many UAAs are either expansive or commercially unavailable. Read More

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February 2021

Application of nanoparticles in chiral analysis and chiral separation.

Chirality 2021 05 1;33(5):196-208. Epub 2021 Mar 1.

Pharmaceutical Chemistry Department, Faculty of Pharmacy, The British University in Egypt, Cairo, Egypt.

Chiral molecules in relation to particular biological roles are stereoselective. Enantiomers differ significantly in their biochemical responses in biological environment. Despite the current advancement in drug discovery and pharmaceutical biotechnology, the chiral separation of some racemic mixtures continues to be one of the greatest challenges, because the available techniques are too costly and time consuming for the assessment of therapeutic drugs in the early stages of development worldwide. Read More

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Emergent stereoselective interactions and self-recognition in polar chiral active ellipsoids.

Sci Adv 2021 Feb 26;7(9). Epub 2021 Feb 26.

International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India.

In many active matter systems, particle trajectories have a well-defined handedness or chirality. Whether such chiral activity can introduce stereoselective interactions between particles is not known. Here, we developed a strategy to tune the nature of chiral activity of three-dimensionally printed granular ellipsoids without altering their shape or size. Read More

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February 2021

Conversion of L-arabinose to L-ribose by genetically engineered Candida tropicalis.

Bioprocess Biosyst Eng 2021 Jun 9;44(6):1147-1154. Epub 2021 Feb 9.

Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea.

L-Ribose, a starting material for the synthesis of L-nucleoside, has attracted lots of attention since L-nucleoside is responsible for the antiviral activities of the racemic mixtures of nucleoside enantiomers. In this study, the L-ribulose-producing Candida tropicalis strain was engineered for the conversion of L-arabinose to L-ribose. For the construction of a uracil auxotroph, the URA3 gene was excised by homologous recombination. Read More

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Capillary electrophoresis and molecular modeling of the chiral separation of aromatic amino acids using α/β-cyclodextrin and 18-crown-6.

Electrophoresis 2021 Feb 4. Epub 2021 Feb 4.

Applied Analytical Chemistry, Faculty of Chemistry, University of Duisburg-Essen, Essen, Germany.

In this work, chiral separation of enantiomers of three amino acids was achieved using capillary electrophoresis technique with α-cyclodextrin (αCD) as a running buffer additive. Only tryptophan has exhibited baseline separation in the presence of αCD, while the enantiomers of the other two amino acids, phenylalanine and tyrosine, were only partially separated. The addition of 18-crown-6 (18C6) as a second additive imparted only slight improvement to the separation of all enantiomers. Read More

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February 2021

Synthesis of Protected 3,4- and 2,3-Dimercaptophenylalanines as Building Blocks for -Peptide Synthesis and Incorporation of the 3,4-Analogue in a Decapeptide Using Solid-Phase Synthesis.

J Org Chem 2021 Feb 24;86(3):2210-2223. Epub 2021 Jan 24.

School of Applied and Interdisciplinary Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.

3,4-Dimercaptophenylalanines and 2,3-dimercaptophenylalanines have been synthesized for the first time by nucleophilic substitution of a protected aminomalonate on 3,4- and 2,3-dimercaptobenzyl bromide derivatives. The dithiol functions were protected as thioketals, and the key precursors, diphenylthioketal-protected dimercaptobenzyl bromides, were synthesized via two distinct routes from either dihydroxy benzoates or toluene-3,4-dithiol. Racemic mixtures of the fully protected amino acids were separated by chiral HPLC into the corresponding enantiomers. Read More

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February 2021

An analysis of Ibuprofen enantiomers in high concentrations of sodium chloride with SARS-CoV-2 main protease.

J Biomol Struct Dyn 2021 Jan 18:1-12. Epub 2021 Jan 18.

Centro de Investigaciones y Transferencia de Villa María (CIT VM), Instituto Académico Pedagógico de Ciencias Humanas, Universidad Nacional de Villa María, Villa María, Argentina.

2020 will be remembered worldwide for the outbreak of Coronavirus disease (COVID-19), which quickly spread until it was declared as a global pandemic. The main protease (Mpro) of SARS-CoV-2, a key enzyme in coronavirus, represents an attractive pharmacological target for inhibition of SARS-CoV-2 replication. Here, we evaluated whether the anti-inflammatory drug Ibuprofen, may act as a potential SARS-CoV-2 Mpro inhibitor, using an study. Read More

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January 2021

Converging Microlens Array Using Nematic Liquid Crystals Doped with Chiral Nanoparticles.

ACS Appl Mater Interfaces 2021 Jan 7;13(3):4574-4582. Epub 2021 Jan 7.

Physics Department, Kent State University, Kent, Ohio 44242, United States.

Nematic liquid crystals of achiral molecules or racemic mixtures of chiral ones form flat films when suspended in submillimeter size grids and submerged under water. Recently, it has been shown (Popov et al., 2017) that films of nematic liquid crystals doped with chiral molecules adopt biconvex lens shapes underwater. Read More

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January 2021

Highly Stable Zr(IV)-Based Metal-Organic Frameworks for Chiral Separation in Reversed-Phase Liquid Chromatography.

J Am Chem Soc 2021 01 24;143(1):390-398. Epub 2020 Dec 24.

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.

Separation of racemic mixtures is of great importance and interest in chemistry and pharmacology. Porous materials including metal-organic frameworks (MOFs) have been widely explored as chiral stationary phases (CSPs) in chiral resolution. However, it remains a challenge to develop new CSPs for reversed-phase high-performance liquid chromatography (RP-HPLC), which is the most popular chromatographic mode and accounts for over 90% of all separations. Read More

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January 2021

2D Ising Model for Adsorption-induced Enantiopurification of Racemates.

Chemphyschem 2021 01 18;22(2):197-203. Epub 2020 Dec 18.

Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA.

Mechanisms for the spontaneous transformation of achiral chemical systems into states of enantiomeric purity have important ramifications in modern pharmacology and potential relevance to the origins of homochirality in life on Earth. Such mechanisms for enantiopurification are needed for production of chiral pharmaceuticals and other bioactive compounds. Previously proposed chemical mechanisms leading from achiral systems to near homochirality are initiated by a symmetry-breaking step resulting in a minor excess of one enantiomer via statistical fluctuations in enantiomer concentrations. Read More

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January 2021

(S)-Thienyl and (R)-Pirydyl phosphonate Derivatives Synthesized by Stereoselective Resolution of Their Racemic Mixtures With (DSM 70403) - Scaling Approaches.

Front Chem 2020 11;8:589720. Epub 2020 Nov 11.

Laboratory of Biotechnology, Department of Biochemistry, Molecular Biology and Biotechnology, Faculty of Chemistry, Wrocław University of Science and Technology, Wrocław, Poland.

was successfully applied as a biocatalyst for the enantioselective resolution of the racemic mixtures of heteroatom phosphonates derivatives, resulting in receiving the following enantiomers: (S)-1-amino-1(2-thienyl)methylphosphonic acid (Product 1) and (R)-1-amino-1-(3'pirydyl) methylphosphonic acid (Product 2). Biological synthesis of both products is reported . Pure (S)-1-amino-1-(2-thienyl)methylphosphonic acid (Product 1) was isolated with a conversion degree of 50% after of biotransformation was conducted on a laboratory scale under moderate conditions (1. Read More

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November 2020

A review on the stereospecific fate and effects of chiral conazole fungicides.

Sci Total Environ 2021 Jan 16;750:141600. Epub 2020 Aug 16.

Recetox, Faculty of Science, Masaryk University, Kamenice 5, Brno 625 00, Czech Republic.

The production and use of chiral pesticides are triggered by the need for more complex molecules capable of effectively combating a greater spectrum of pests and crop diseases, while sustaining high production yields. Currently, chiral pesticides comprise about 30% of all pesticides in use; however, some pesticide groups such as conazole fungicides (CFs) consist almost exclusively of chiral compounds. CFs are produced and field-applied as racemic (1:1) mixtures of two enantiomers (one chiral center in the molecule) or four diastereoisomers, i. Read More

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January 2021

Adsorption of Chiral [5]-Aza[5]helicenes on DNA Can Modify Its Hydrophilicity and Affect Its Chiral Architecture: A Molecular Dynamics Study.

Materials (Basel) 2020 Nov 7;13(21). Epub 2020 Nov 7.

Dipartimento di Ingegneria e Scienze Applicate, Università degli Studi di Bergamo, 24044 Bergamo, Italy.

Helicenes are interesting chiral molecules without asymmetric carbon atoms but with intrinsic chirality. Functionalized 5-Aza[5]helicenes can form non-covalent complexes with anticancer drugs and therefore be potential carriers. The paper highlights the different structural selectivity for DNA binding for two enantiopure compounds and the influence of concentration on their adsorption and self-aggregation process. Read More

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November 2020

Immobilization of 6-O-α-maltosyl-β-cyclodextrin on the surface of black phosphorus nanosheets for selective chiral recognition of tyrosine enantiomers.

Mikrochim Acta 2020 Nov 3;187(11):636. Epub 2020 Nov 3.

College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, Hunan, China.

A novel chiral sensing platform, 6-O-α-maltosyl-β-cyclodextrin (Mal-βCD)-based film, is proposed for selective electrochemical recognition of tyrosine (Tyr) enantiomers. Black phosphorus nanosheets (BP NSs) and Mal-βCD modified glassy carbon electrode (Mal-βCD/BP NSs/GCE) were prepared by a layer-to-layer drop-casting method, and the platform was easy to fabricate and facile to operate. It is proposed that the amino and hydroxyl groups of the Tyr enantiomers and the chiral hydroxyl groups of Mal-βCD selectively form intermolecular hydrogen bonds to dominate effective chiral recognition. Read More

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November 2020

Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts.

Angew Chem Int Ed Engl 2021 Jan 27;60(1):247-251. Epub 2020 Oct 27.

Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany.

A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Read More

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January 2021