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PubMed Journals Articles About "Chiral Technologies, Inc" - Page: 3 RSS

16:26 EDT 23rd October 2018 | BioPortfolio

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Showing "Chiral Technologies" PubMed Articles 51–75 of 2,400+

Umpolung of Imines Enables Catalytic Asymmetric Regio-Reversed 3+2 Cycloadditions of Iminoesters with Nitroolefins.

A copper-catalyzed regio-reversed asymmetric [3+2] cycloaddition of iminoesters with nitroolefins was disclosed for the first time. This protocol allows the facile synthesis of polysubstituted chiral pyrrolidines bearing at least one chiral quaternary center in high yields with excellent regio-, diastereo- and enantioselectivities. The application of chiral P,S-ligands and the unique effect of α-aryl groups on the iminoesters were the keys to the success of this method. The practicality and versatility of ...


Stereoselective HPLC separation of alvimopan on cellulose-based immobilized polysaccharide as a chiral stationary phase.

Chiral separation by normal phase high performance liquid chromatography is one of the most powerful technique to quantify the chiral purity of the compounds. In this study, a novel, simple, and specific analytical method was proposed to ascertain the chiral purity of alvimopan (ALV). The normal phase HPLC method was developed based on cellulose tris (3,5-dichlorophenylcarbamate) stationary phase. The separation of ALV isomers achieved by using column CHIRALPAK IC (250 × 4.6 mm, 5 μm), mobile phase n-...

Formation of Chiral Allylic Ethers via an Enantioselective Palladium-Catalyzed Alkenylation of Acyclic Enol Ethers.

This report details a palladium-catalyzed process to access high-ly functionalized optically active allylic aryl ethers. A number of electron-deficient alkenyl triflates underwent enantio- and site-selective coupling with acyclic aryl enol ethers in the presence of a chiral palladium catalyst. This transform provides chiral allylic ether products in high yields and excellent enanti-omeric ratios furnishing a unique disconnection to incorporate heteroatoms at a stereocenter. Finally, the applicability of the...


Chiral Inductions in Excited State Reactions: Photodimerization of Alkyl 2-Naphthoates as a Model.

Enantioselectivity in organic transformations continues to be a topic major interest in organic photochemistry. In the last decade, synergistic combination of photocatalysis and organocatalysis has emerged as a powerful strategy to gain enantioselectivity in photochemical reactions, and remarkable achievements have been obtained. In this strategy the asymmetric induction is provided in ground state. In contrast, in the conventional enantioselective photochemistry the chiral induction is controlled in electr...

Chiral Transmission to Cationic Polycobaltocenes over Multiple Length Scales Using Anionic Surfactants.

Chiral polymers are ubiquitous in nature, and the self-assembly of chiral materials is a field of widespread interest. In this paper, we describe the formation of chiral metallopolymers based on poly(cobaltoceniumethylene) ([PCE] ), which have been prepared through oxidation of poly(cobaltocenylethylene) (PCE) in the presence of enantiopure N-acyl-amino-acid-derived anionic surfactants, such as N-palmitoyl-l-alanine (C-l-Ala) and N-palmitoyl-d-alanine (C-d-Ala). It is postulated that the resulting metallopo...

1/2(e^{2}/h) Conductance Plateau without 1D Chiral Majorana Fermions.

We address the question about the origin of the 1/2(e^{2}/h) conductance plateau observed in a recent experiment on an integer quantum Hall (IQH) film covered by a superconducting (SC) film. Since one-dimensional (1D) chiral Majorana fermions on the edge of the above device can give rise to the half quantized plateau, such a plateau is regarded as conclusive evidence for the chiral Majorana fermions. However, in this Letter we give another mechanism for the 1/2(e^{2}/h) conductance plateau. We find the 1/2(...

Nanoimprinted chiral plasmonic substrates with three-dimensional nanostructures.

We report a large-area fabrication method to prepare chiral substrates patterned with arrays of multilayer, three-dimensional nanostructures using a combination of nanoimprint lithography and glancing angle deposition. Several structures are successfully fabricated using this method, including L-shaped, twisted arc and tri-layer twisted Au nanorod structures, demonstrating its generality. As one typical example, arrays of L-shaped nanostructures, consisting of two layers of orthogonally oriented Au nanorods...

Bottom-Up Synthesis of Heteroatom-Doped Chiral Graphene Nanoribbons.

Bottom-up synthesis of graphene nanoribbons (GNRs) has significantly advanced during the past decade, providing various GNR structures with tunable properties. The synthesis of chiral GNRs, however, has been underexplored, and only limited to (3,1)-GNRs. We report herein the surface-assisted synthesis of the first heteroatom-doped chiral (4,1)-GNRs from the rationally designed precursor 6,16-dibromo-9,10,19,20-tetraoxa-9a,19a-diboratetrabenzo[ a,f,j,o]perylene. The structure of the chiral GNRs has been veri...

Development of C-Symmetric Chiral Bifunctional Triamines: Synthesis and Application in Asymmetric Organocatalysis.

The synthesis and application of a newly designed C-symmetric chiral bifunctional triamine family ( C-CBT) is reported. These enantiopure chiral triamine scaffolds can be accessed in multigram amounts from simple amino acids while avoiding chromatographic purification. As a proof of principle, C-CBT has been studied in the aldol reaction of cyclic ketones with isatins, with the target tertiary alcohols being formed in a highly efficient manner. Catalyst recovery by simple extraction techniques and subsequen...

Optimization of a two-dimensional liquid chromatography-supercritical fluid chromatography-mass spectrometry (2D-LC-SFS-MS) system to assess "in-vivo" inter-conversion of chiral drug molecules.

Enantioselective analysis is an essential requirement during the pharmaceutical development of chiral drug molecules. In pre-clinical and clinical studies, the Food and Drug Administration (FDA) mandates the assessment of "in vivo" inter-conversion of chiral drugs to determine their physiological effects. In-vivo analysis of the active pharmaceutical ingredient (API) and its potential metabolites could be quite challenging due to their low abundance (ng/mL levels) and matrix interferences. Therefore, highly...

Asymmetric 3 + 2 Cycloaddition Employing N, N'-Cyclic Azomethine Imines Catalyzed by Chiral-at-Metal Rhodium Complex.

An efficient asymmetric 1,3-dipolar cycloaddition of α,β-unsaturated 2-acyl imidazoles with N, N'-cyclic azomethine imines catalyzed by a chiral-at-metal rhodium complex is reported. The corresponding N, N'-bicyclic pyrazolidine derivatives with three contiguous tertiary stereocenters were obtained in good yields (up to 99%) with excellent stereoselectivities (>20:1 dr and >99% ee). Remarkably, as little as 0.5 mol % of a chiral Rh(III) complex can promote a gram-scale reaction with excellent yield and en...

pseudo1Catenane-Type Pillar5thiacrown Whose Planar Chiral Inversion is Triggered by Metal Cation and Controlled by Anion.

Chiral inversion of single molecules has been a challenging task because chirality information controls structures and func-tions of various molecules, artificial nanostructures, DNA, and proteins. Herein we present a pseudo[1]catenane-type mole-cule whose planar chiral inversion is driven by a metal ion under the control of anions for the first time. Considering an in-out equilibrium of a fused thiacrown and the soft metal binding, pillar[5]thiacrown ( rac-L) was synthesized. Two planar-chiral enantiomers ...

Homochiral Double Helicates Based on Cyclooctatetrathiophene: Chiral Self-sorting with the Intramolecular S···N Interaction.

We have designed and synthesized homochiral double helicates that are constructed via Ag-induced supramolecular self-sorting of saddle-shaped cyclooctatetrathiophene-based pyridine ligands. The intramolecular S···N interaction leads the thiophene and pyridine rings of ligands 1 and 2 to be in coplanar and syn-locked structures. In the presence of Ag+, the racemic ligands 1 and 2 only afforded homochiral double helicates, indicating effective chiral self-sorting process under the influence of the S···N...

Ni(II)-catalyzed asymmetric alkenylations of ketimines.

Chiral allylic amines are not only present in many bioactive compounds, but can also be readily transformed to other chiral amines. Therefore, the asymmetric synthesis of chiral allylic amines is highly desired. Herein, we report two types of Ni(II)-catalyzed asymmetric alkenylation of cyclic ketimines for the preparation of chiral allylic amines. When ketimines bear alkyl or alkoxycarbonyl groups, the alkenylation gives five- and six-membered cyclic α-tertiary allylic amine products with excellent yields ...

A chiral sensor based on weak measurement for the determination of Proline enantiomers in diverse measuring circumstances.

A new chiral sensor based on weak measurement to accurately measure the optical rotation (OR) has been developed for the estimation of a trace amount of chiral molecule. With the principle of optical weak measurement in frequency domain, the central wavelength shift of output spectra is quantitatively relative to the angle of preselected polarization. Hence, a chiral molecule (e.g., L-amino acid, or D-amino acid) can be enantioselectively determined by modifying the preselection angle with the OR, which wil...

Probing Adsorption Behaviors of BSA onto Chiral Surfaces of Nanoparticles.

Chiral properties of nanoscale materials are of importance as they dominate interactions with proteins in physiological environments; however, they have rarely been investigated. In this study, a systematic investigation is conducted for the adsorption behaviors of bovine serum albumin (BSA) onto the chiral surfaces of gold nanoparticles (AuNPs), involving multiple techniques and molecular dynamic (MD) simulation. The adsorption of BSA onto both L- and D-chiral surfaces of AuNPs shows discernible difference...

Enantiodivergent Synthesis of Allenes by Point to Axial Chirality Transfer.

An enantiodivergent method for the synthesis of multiply substituted allenes is described. Highly enantioenriched, point chiral boronic esters were synthesized by homologation of lithiated carbamates with α-seleno vinyl boronic esters and eliminated to form axially chiral allene products. By employing either oxidative or alkylative conditions, both syn- and anti-elimination could be achieved with complete stereospecificity. The process enables the synthesis of either (M) or (P) allenes from a single isomer...

Asymmetric Synthesis of Chiral Spiroketal Bisphosphine Ligands and Their Application in Enantioselective Olefin Hydrogenation.

A series of chiral spiroketal bisphosphine ligands containing 1,1'-spirobi(3H,3'H)isobenzofuran backbones was accessed through asymmetric synthesis and subsequently tested in enantioselective Rh-catalyzed hydrogenation of α-dehydroamino acid esters. The ligand providing the highest enantioselectivity (up to 99.5%) was obtained in seven steps in an overall 38% yield. The synthesis could be performed on gram-scale and no kinetic resolution of enantiomers is required. Overall, the developed ligand provides an...

Impact of Optical Purity on Light Harvesting Property in Supramolecular Nanofibers.

Supramolecular ordering and orientation of chromophores are tremendously accomplished in the photosynthetic light harvesting complexes, which are crucial for long-range transfer of collected solar energy. We herein demonstrate the importance of optical purity on the organization of chromophoric chiral molecules for the efficient energy migration. Enantiomeric bichromophoric compounds, which self-assemble into nanofibers capable of chiral recognition, were mixed to form supramolecular co-assemblies with vari...

Enantioselective Halo-oxy- and Halo-azacyclizations Induced by Chiral Amidophosphate Catalysts and Halo-Lewis Acids.

Catalytic enantioselective halocyclization of 2-alkenylphenols and enamides have been achieved through the use of chiral amidophosphate catalysts and halo-Lewis acids. DFT calculations suggested that the Lewis basicity of the catalyst played an important role in the reactivity and enantioselectivity. The resulting chiral halogenated chromans can be transformed to α-tocopherol, α-tocotrienol, Daedalin A and Englitazone in short steps. Furthermore, a halogenated product with an unsaturated side chain may pr...

Adoption of Stroke Rehabilitation Technologies by the User Community: Qualitative Study.

Using technology in stroke rehabilitation is attractive. Devices such as robots or smartphones can help deliver evidence-based levels of practice intensity and automated feedback without additional labor costs. Currently, however, few technologies have been adopted into everyday rehabilitation.

Enantioselectivity in biotransformation and bioaccumulation processes of typical chiral contaminants.

Chirality is a critical topic in the medicinal and agrochemical fields. One quarter of all agrochemicals was chiral in 1996, and this proportion has increased remarkably with the introduction of new compounds over time. Despite scientists have made great efforts to probe the enantiomeric selectivity of chiral chemicals in the environment since early 1990s, the different behaviours of individual enantiomers in biologically mediated processes are still unclear. In the present review, we highlight state-of-the...

Solvent polarity effects on supramolecular chirality of a polyfluorene-thiophene copolymer.

This study demonstrates the supramolecular chirality control of a conjugated polymer via solvent polarity. We designed and synthesized a chiral polyfluorene-thiophene copolymer having two different chiral side chains at the 9-position of the fluorene unit. Chiral cyclic and alkyl ethers with different polarities were selected as the chiral side chains. The sign of the circular dichroism spectra in the visible wavelength region was affected by the solvent system, resulting from the change of supramolecular s...

Chiral Atropisomeric Indenocorannulene Bowls: Critique of Cahn-Ingold-Prelog Conception of Molecular Chirality.

Chiral corannulenes abound, but suffer generally from configurational lability associated with bowl-to-bowl inversion, thus obviating questions of stereogenicity and stereo element construction. In contrast, peri-annulated corannulenes show greatly increased barriers for bowl-to-bowl inversion, specifically indenocorannulenes invert on a time scale too slow to observe by normal NMR methods and raise the possibility of creating chiral atropisomeric bowl-shaped aromatics. Monosubstituted indenocorannulenes co...

Remote Central-to-Axial Chirality Conversion: Direct Atroposelective Ester to Biaryl Transformation.

A strategy for the remote central-to-axial chirality conversion by simultaneous planarization of an encoding and a transient stereocenter is presented. Based on a diastereoselective double addition of a chiral 1,5-bifunctional organomagnesium alkoxide reagent to a broad range of aryl ester substrates, axially chiral biaryls are directly obtained upon in situ reduction. Various structurally distinct atropisomeric biaryl silanes that serve as valuable chiral biaryl anion surrogates are accessible in one step ...


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