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A rapid, simple, reliable, and environment‐friendly method for the residue analysis of the enantiomers of four chiral fungicides including hexaconazole, triadimefon, tebuconazole, and penconazole in water samples was developed by dispersive liquid–liquid microextraction (DLLME) pretreatment followed by chiral high‐performance liquid chromatography (HPLC)‐DAD detection. The enantiomers were separated...
A simple and straightforward four‐step synthesis of novel diastereomeric L‐phenylalanine‐derived pyrazolidin‐3‐ones is described. The absolute configuration of the novel C(5) stereogenic centre has been unambiguously determined by single crystal X‐ray analysis and via chemical interconversions. A series of novel thiourea derived pyrazolidinones have been prepared and tested as potential organocatalysts...
The aim of the present study was to elucidate the differences in the plasma concentration of two enantiomers of donepezil in Chinese patients with Alzheimer's disease (AD) and investigate in vitro stereoselective metabolism and transport. Donepezil enantiomers were separated and determined by LC‐MS/MS using D5‐donepezil as an internal standard on a Sepax Chiralomix SB‐5 column. In vitro stereoselective...
Dirhodium metallopeptides have been developed as selective catalysts for asymmetric cyclopropanation reactions. A selective ligand sequence has been identified by screening on‐bead metallopeptide libraries in a 96‐well plate format. Efficient ligand synthesis and screening allows a 200‐member library to be created and assayed in less than three weeks. These metallopeptides catalyze efficient cyclopropanation...
The direct aldol reaction between aryl methyl ketones with aromatic aldehydes in the presence of tetrachlorosilane and a catalytic amount of a chiral bithiophene diphosphine oxide was studied; the product of double aldol addition was isolated as diacetate in good diastereoselectivity (up to 95:5) and enantioselectivities up to 91%. The reaction with heteroaromatic aldehydes was also investigated leading...
The synthesis of new bitropone derivatives, namely, 3,3'‐biphenyl‐2,2'‐bitropone and 7,7’‐biphenyl‐2,2'‐bitropone, are reported. Isolation of enantiomers arising from restricted rotation around the C‐C bond connecting the tropone moieties was attempted by means of chiral high performance liquid chromatography (HPLC). No separation was obtained for 7,7’‐biphenyl‐2,2'‐bitropone. For 3,3'‐biphenyl‐2,2'‐bitropone,...
Salicylidenimine palladium(II) complexes trans‐Pd(O,N)2 adopt step and bowl arrangements. A stereochemical analysis subdivides 52 compounds into 41 step and 11 bowl types. Step complexes with chiral N‐substituents and all the bowl complexes induce chiral distortions in the square planar system, resulting in Δ/Λ configuration of the Pd(O,N)2 unit. In complexes 1, 2, 3, 4, 5, 6 with enantiomerically...
A series of single isomers tetrahydro‐β‐carboline diketopiperazines were stereoselectively synthesized starting from l‐tryptophan methyl ester hydrochloride and six aldehydes through a four‐step reaction including Pictet‐Spengler reaction, crystallization‐induced asymmetric transformations (CIAT), Schotten‐Baumann reaction, and intramolecular ester amidation. The chemical structures were characterized...
Protein–protein interactions are crucial for signal transductions required for cell differentiation and proliferation. Their modulation is therefore key to the development of therapeutic alternatives, particularly in the context of cancer. According to literature data, the polyproline‐rich nuclear receptor coactivators PNRC and PNRC2 interact with estrogen receptor (ERα) through their PxxP SH3‐binding...
Tolperisone and eperisone used as muscle relaxants possess one chiral center each and exist as two optical isomers for each drug. Therefore, enantioselective assays to measure each enantiomer in biological matrices are of great importance. In the present study a simple and complete reverse‐phase liquid chromatography tandem mass spectrometric method for separation and enantioselective determination...
It has been recognized that quantum‐chemical predictions of dispersive (nonresonant) chiroptical phenomena are exquisitely sensitive to the periphery of the electronic wavefunction. To further elaborate and potentially exploit this assertion, linear‐response calculations of specific optical rotation were performed within the framework of density‐functional theory (DFT) by augmenting small basis sets...
An easy‐to‐prepare chiral CE method for the enantiomeric separation of 13 new amphetamine‐like designer drugs, using CDs as chiral selectors, was developed. Sulfated‐β‐CD was found to be the best chiral selector among the three used (sulfated‐β‐CD, caroboxymethyl‐β‐CD, dimethyl‐β‐CD). The separation of the analytes was achieved in a fused‐silica gel capillary at 20 °C using an applied voltage of +25...
An algorithm is employed to retrieve the differential bond polarizabilities of the C‐C bonds from the Raman optical activity (ROA) spectrum of (−)α‐pinene. (−)α‐pinene possesses two asymmetric centers (carbon atoms) and a local mirror symmetry. These differential bond polarizabilities show the characteristics of the asymmetry around the asymmetric carbons with respect to the mirror reflection. This...
Ornithine (Orn) plays an essential role in the metabolism of plant cells through incorporation in polyamines biosynthesis, the urea cycle and nitrogen metabolism. Herein, we show that Orn enantiomers have different effects on anti‐oxidant enzymes activities, polyamines and proline biosynthesis and also an alleviation effect of osmotic stresses on tobacco cells. The type of stress has a significant...
UV, circular dichroism (CD), fluorescence and circularly polarized luminescence (CPL) spectra were recorded for a set of four related [2.2.1] bicyclic compounds ((1S,4S)‐and (1R,4R)‐1,7,7‐trimethylbicyclo[2.2.1]heptan‐2‐one, namely (1S)‐ and (1R)‐camphor (1), (1S,4R)‐4,7,7‐trimethylbicyclo[2.2.1]hept‐5‐en‐2‐one, (1S)‐dehydro‐epicamphor (2), (1S,4S)‐1,7,7‐trimethylbicyclo[2.2.1]heptane‐2,5‐dione, (1...
In this study we addressed the role of chirality in the biological activity of RC-33, recently studied by us in its racemic form. An asymmetric synthesis procedure was the first experiment, leading to the desired enantioenriched RC-33 but with an enantiomeric excess (ee) not good enough for supporting the in vitro investigation. An enantioselective high‐performance liquid chromatography (HPLC) procedure...
Racemic mixtures of six Tröger's base derivatives were separated by chiral nonaqueous capillary electrophoresis. The separation protocol was optimized first for suitable solvents. Then the applicability of various salts dissolved in organic solvents and their mixtures was evaluated. As chiral selectors β‐cyclodextrin and heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin at various concentrations were used...
Dimethylaluminum triflate‐mediated activation of tetrafluorobenzoates of enantiomerically pure bromohydrins results in enantiospecific polyene cyclizations. The initiation of cyclization by enantiomerically pure bromonium ions and subsequent propagation is not subject to catastrophic erosion of enantiomeric purity by any intramolecular or intermolecular bromonium ion‐to‐alkene transfer. Chirality...
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