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Chirality
Kinds of Chirality Terms modified by Chirality Selected AbstractsSynthesis, Coordination and Catalytic Utility of Novel Phosphanyl,ferrocenecarboxylic Ligands Combining Planar and Central ChiralityEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Martin Lama Abstract The chiral ferrocene derivative (R,Rp)-2-[1-(diphenylphosphanyl)ethyl]ferrocenecarboxylic acid (1) is prepared together with selected derivatives resulting from modification at the phosphane moiety [P -oxide (5) and P -sulfide (4)] and the carboxyl group {amides bearing benzyl (6) and (R)- or (S)-1-phenylethyl substituents [(R)- 7 and (S)- 7] at the amide nitrogen atom}. Acid 1 and amide 6 are studied as ligands in rhodium and palladium complexes. Bridge cleavage of the dimer [{Rh(,-Cl)Cl(,5 -C5Me5)}2] with 1 gives [RhCl2(,5 -C5Me5)(1 -,P)] (9) containing P-monodentate 1, which undergoes smooth conversion to the (phosphanylalkyl)ferrocenecarboxylato complex [RhCl(,5 -C5Me5){Fe(,5 -C5H5)(,5 -C5H3 -1-CH(Me)PPh2 -2-COO-,2O,P}] (10) upon treatment with silica gel or alumina. Yet another O,P -chelate complex,[Rh{Fe(,5 -C5H5)(,5 -C5H3 -1-CH(Me)PPh2 -2-COO-,2O,P}(CO)(PCy3)] (11; Cy = cyclohexyl) is obtained directly by an acid-base reaction between the acetylacetonato complex [Rh(acac)(CO)(PCy3)] and 1. Amide 6 reacts with [{Pd(,-Cl)(,3 -C3H5)}2] to give the expected phosphane complex [PdCl(,3 -C3H5)(6 -,P)] (12), while the replacement of the cyclooctadiene (cod) ligand in [PdCl(Me)(cod)] affords the chelate complex [PdCl(Me)(6 -,2O,P)] (13). All compounds are characterised by spectroscopic methods and the solid-state structures of 5, 9, 11, 13, (R,Sp)-2-[1-(diphenylphosphoryl)ethyl]-1-[N -(R)-(1-phenylethyl)carbamoyl]ferrocene [(R)- 8; phosphane oxide from (R)- 7], and the synthetic precursors (R,Sp)-1-bromo-2-[1-(diphenylphosphanyl)ethyl]ferrocene (2) and (R,Sp)-1-bromo-2-[1-(diphenylthiophosphoryl)ethyl]ferrocene (3) determined by single-crystal X-ray diffraction. The catalytic properties of 1 and the amides are probed in enanatioselective rhodium-catalysed hydrogenation and palladium-catalysed asymmetric allylic alkylation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] From Central to Axial to Central Chirality: Enantioselective Construction of the trans -4,5,9,10-Tetrahydroxy-9,10-dihydrophenanthrene SystemEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2007Georgi Stavrakov Abstract Enantioselective synthesis of the core trans -4,5,9,10-tetrahydroxy-9,10-dihydrophenanthrene parent system of the antibiotics benanimicin, pradimicin and FD 594 has been accomplished. The synthesis employs a chiral tether approach and makes use of efficient central to axial to central chirality transfer. Key to success was an "imine-directed" atropdiastereoselective Ullmann coupling under mild reaction conditions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Guest-Induced Chirality in the Ferrimagnetic Nanoporous Diamond Framework Mn3(HCOO)6,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2007B. Zhang Abstract Chiral magnets are obtained by inclusion of chiral guest molecules into the channels of an achiral nanoporous ferrimagnet consisting of the Mn3(HCOO)6 (1) framework. Insertion of the R or the S enantiomer of 2-chloropropan-1-ol (CH3C*HClCH2OH) in the chiral pores of the previously emptied framework (space group P21/c) results in the two corresponding chiral solids (1R and 1S, space group P21), while insertion of a racemic mixture of the two enantiomers retains the achirality of the host for the meso solid (1RS, space group P21/c). The R guest is ordered in the M channels while the S guest is ordered in the P channels. In contrast, the R guests in the P channels and the S guests in the M channels are disordered on two crystallographic orientations. For the racemic mixture of the two enantiomers in 1RS, random disorder of guests in both channels is observed. Thus, the localization of the guest molecule depends on the nature of the surface to recognize the guest of a particular chirality. The guest inclusion compounds are thermally stable. The 1R and 1S compounds are optically active. All the compounds adopt a ferrimagnetic ground state. Compared to the host framework of 1 without guest, the Curie temperature decreases for both 1R and 1S but increases for 1RS. The additional interactions between the framework and the inserted guest alcohols strengthen the lattice via hydrogen bonds and other electrostatic forces, and it might account for the significant lowering of the lattice contribution as well as the magnetic component to the specific heat capacity upon guest loading. [source] A Thiourea-Oxazoline Library with Axial Chirality: Ligand Synthesis and Studies of the Palladium-Catalyzed Enantioselective Bis(methoxycarbonylation) of Terminal OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Ying-Xiang Gao Abstract We report herein the synthesis of novel chiral S,N-heterobidentate thiourea-oxazoline ligands and their application to palladium-catalyzed enantioselective bis(methoxycarbonylation)s of terminal olefins under mild conditions. Copper salts were found to play multiple roles in this reaction. Substituted 2-phenylsuccinates were obtained in >90% yield and up to 84% ee under optimized conditions. [source] Control of Induced Chirality in Optically Active Poly(N-propargylcarbamate) Films by Solvent VaporMACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2009Toshiyuki Fukushima Abstract Chiral polyethyne derivatives with lyotropic liquid-crystalline properties are found to be able to self-assemble, forming two chiral organizations with opposite handedness in solid thin films by selection of the casting solvent and its concentration. After the film preparation, chiral organization could also be induced by simple exposure to an appropriate organic solvent's vapor for several minutes without thermal treatment. Furthermore, irreversible inversion of the handedness of the chiral organization in the film could be achieved by exposure to solvent vapor. [source] Chirality in liquid crystals.ACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2002Christian Bahr., Edited by Heinz-Siegfried Kitzerow First page of article [source] Chirality at the Nanoscale.ANGEWANDTE CHEMIE, Issue 8 2010Materials, Nanoparticles, Surfaces, more. Wiley-VCH, Weinheim 2009. 418,S., geb., 149.00,,.,ISBN 978-3527320134 [source] Control of the Helicity of Poly(phenylacetylene)s: From the Conformation of the Pendant to the Chirality of the Backbone,ANGEWANDTE CHEMIE, Issue 8 2010Iria Louzao Dr. Auswahl der Gangrichtung: Das Konformerengleichgewicht der Substituenten eines Poly(phenylacetylens), und mit diesem die Helizität des Polymers, lässt sich reversibel verändern. Durch Komplexierung mit Metallkationen wie Ba2+ oder einen Wechsel in der Lösungsmittelpolarität kann die gewünschte Gangrichtung ausgewählt werden. Die mechanistische Grundlage dieses Phänomens wird im Detail erklärt. [source] On the Chirality of Self-Assembled DNA Octahedra,ANGEWANDTE CHEMIE, Issue 4 2010Yu He Was spricht gegen windschief? Ein rationaler Ansatz ermöglichte es, die Selbstorganisation eines DNA-Oktaeders zu programmieren (siehe Struktur; der Farbgradient deutet den Abstand vom Oktaederzentrum an). Eine genaue Strukturuntersuchung ergab, dass die Assoziation der Nanoobjekte stereoselektiv war (die Ansicht einer Ecke zeigt den schiefen Hohlraum, der die Bestimmung der Chiralität der Oktaeder ermöglichte). [source] Arylimidovanadium(V) Complexes for a Tridendritic Centrosymmetric Structural Motif or Axial Chirality,ANGEWANDTE CHEMIE, Issue 1 2010Toshiyuki Moriuchi Dr. Wahlweise: Bei der Eintopfreaktion von Anilinderivaten mit VO(OiPr)3 in Gegenwart von NaH entsteht entweder dreikerniges Arylimidovanadium(V)-triisopropoxid mit einer tridendritischen zentrosymmetrischen Struktur (links im Bild) oder axial-chirales zweikerniges Arylimidovanadium(V)-triisopropoxid (rechts), bei dem die Selbstorganisation eine hoch geordnete Molekülanordnung im Festkörper zur Folge hat. [source] Vortexes and Nanoscale Chirality,ANGEWANDTE CHEMIE, Issue 1 2010Alessandro D'Urso Dr. J-Aggregate antworten dynamisch auf durch Rühren erzeugte Strudel. Das CD-Signal kehrt sich mit der Rührrichtung um, und seine Intensität nimmt zu. Bei längerem Rühren lagern sich chirale Aggregate an der Küvettenwand ab, deren Chiraliät von der Rührrichtung abhängt. Das Rühren verschiebt das Gleichgewicht einer racemischen Mischung zu der durch die Rührrichtung gewählten (und bevorzugten) Seite (siehe Bild; CW,CCW: Rühren im bzw. gegen den Uhrzeiger). [source] Innentitelbild: Switching the Chirality of the Metal Environment Alters the Coordination Mode in Designed Peptides (Angew. Chem.ANGEWANDTE CHEMIE, Issue 40 200940/2009) So wie Eisenbahnweichen die Richtung eines ankommenden Zugs ändern, ändert der Chiralitätswechsel bei einem einzigen Rest im Innern einer de,novo entworfenen dreisträngigen Doppelwendel die Metallbindefähigkeit des Peptids und die Position und Koordinationsumgebung des Metallions drastisch. In der Zuschrift von Pecoraro et,al. auf S.,7507,ff. wird die Bindung von CdII an die L - und D -Enantiomere eines thiolhaltigen Penicillamins durch lösungsspektroskopische Studien und Röntgenbeugung analysiert. [source] Switching the Chirality of the Metal Environment Alters the Coordination Mode in Designed Peptides,ANGEWANDTE CHEMIE, Issue 40 2009Außenseiter machen sich bemerkbar: Wird die Chiralität einer einzigen Aminosäureebene in einer dreisträngigen Doppelwendel umgekehrt (siehe Bild), bewirkt dies nach röntgenographischen Untersuchungen kaum eine Störung des ,-helicalen Rückgrats der Struktur. Dagegen werden laut spektroskopischen Studien zur Bindung von Cadmium durch diesen Chiralitätswechsel die Koordinationsumgebung und die Bindungsstelle drastisch verändert. [source] Trityl Ethers: Molecular Bevel Gears Reporting Chirality through Circular Dichroism Spectra,ANGEWANDTE CHEMIE, Issue 38 2009Jacek, ciebura Mehr als nur eine Schutzgruppe: Die Tritylgruppe wird in Tritylethern von der Chiralität eines Alkylsubstituenten beeinflusst, wie aus den CD-Spektren solcher tritylgeschützten chiralen Alkohole hervorgeht. Das Trityl-CD-Verfahren gibt Einblicke in die Struktur und Funktion chiraler molekularer Getriebe und belegt den Zusammenhang zwischen der Absolutkonfiguration von Molekülen und dem Muster ihres Cotton-Effekts. [source] Quantifying End-to-End Conformational Communication of Chirality through an Achiral Peptide Chain,ANGEWANDTE CHEMIE, Issue 32 2009Jonathan Clayden Prof. Erfolgreich kommuniziert: Zwei diastereotope Protonen, die mehr als 60 Bindungen vom nächsten Chiralitätszentrum entfernt sind, liefern Signale eines AB-Systems, was für eine gut geordnete Helix der dazwischenliegenden Struktur spricht. Aus der Abnahme der Anisochronie lässt sich die lineare Persistenz einer Helix aus achiralen Aminosäuren quantifizieren: Nur 3.5,% des Chiralitätseinflusses geht pro achiralen Rest verloren. [source] Hani Amouri and Michel Gruselle Chirality in transition metal chemistry: molecules, supramolecular assemblies and Materials Wiley, 2008, 260 pp. £37.50/,46.90 0470060549 ISBN-13 9780470060544APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2009Nick Fletcher No abstract is available for this article. [source] Cover Picture: Biotechnology Journal 5/2006BIOTECHNOLOGY JOURNAL, Issue 5 2006Article first published online: 11 MAY 200 Cover illustration: Chirality is omnipresent in nature: Many compounds contain an asymmetric center and thus can occur in two non-superimposable mirror-image forms (enantiomers). The two enantiomers of a chiral compound often have dramatically different effects, as exemplified by the thalidomid catastrophe. Therefore, only one enantiomer is needed for the production of active substances in the pharmaceutical or agricultural industry. It is an important aspect in white biotechnology, to take advantage of highly specific catalysts of (micro-) biological origin for the synthesis of enantiopure compounds. Biocatalysis indeed is a highly efficient process and an example of environmentally friendly, ,green' chemistry, requiring relatively low energy inputs, mild solvents and generating minimal byproducts. Image © Wacker. [source] ChemInform Abstract: Polarity and Chirality in Uranyl Borates: Insights into Understanding the Vitrification of Nuclear Waste and the Development of Nonlinear Optical Materials.CHEMINFORM, Issue 33 2010Shuao Wang Abstract The compounds (IV,VII) and (IX,XII) are synthesized with various Na(Tl):U:B molar ratios using H3BO3 as a reactive flux, and their structures are determined by single crystal XRD. [source] ChemInform Abstract: Helices, Chirality and Interpenetration: The Versatility and Remarkable Interconversion of Silver,Copper Cyanide Frameworks.CHEMINFORM, Issue 48 2009Ann M. Chippindale Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Matching the Chirality of Monodentate N-Heterocyclic Carbene Ligands: A Case Study on Well-Defined Palladium Complexes for the Asymmetric ,-Arylation of Amides.CHEMINFORM, Issue 19 2009Xinjun Luan Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: 2-Phospha[3]ferrocenophanes with Planar Chirality: Synthesis and Use in Enantioselective Organocatalytic [3 + 2] Cyclizations.CHEMINFORM, Issue 9 2009Arnaud Voituriez Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Oxidation of Methylpiperidine Derivatives with Regard to Chirality.CHEMINFORM, Issue 13 2008Hans Moehrle Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Enantioselective Nucleophilic Addition to N-(2-Pyridylsulfonyl)imines by Use of Dynamically Induced Chirality.CHEMINFORM, Issue 13 2006Hideki Sugimoto Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A [5]HELOL Analogue that Senses Remote Chirality in Alcohols, Phenols, Amines, and Carboxylic Acids.CHEMINFORM, Issue 7 2006David Zhigang Wang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF. [source] Synthesis of Novel P-Ketimine Bidentate Ferrocenyl Ligands with Central and Planar Chirality and Comparison in the Catalytic Activity Between P-Ketimine and P-Aldimine.CHEMINFORM, Issue 11 2004Xiangping Hu Abstract For Abstract see ChemInform Abstract in Full Text. [source] Facile Axial Chirality Control by Using a Precursor with Central Chirality.CHEMINFORM, Issue 11 2003Application to the Preparation of New Axially Chiral Diphosphine Complexes for Asymmetric Catalysis. Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Highly Stereospecific Conversion of C-Centrochirality of a 3,4-Dihydro-2H-1,1,-binaphthalen-1-ol into Axial Chirality of a 3,4-Dihydro-1,1,-binaphthalene.CHEMINFORM, Issue 8 2002Tetsutaro Hattori Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Dynamic Supramolecular Polymers Based on Benzene-1,3,5-tricarboxamides: The Influence of Amide Connectivity on Aggregate Stability and Amplification of ChiralityCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2010Patrick Abstract N-Centred benzene-1,3,5-tricarboxamides (N-BTAs) composed of chiral and achiral alkyl substituents were synthesised and their solid-state behaviour and self-assembly in dilute alkane solutions were investigated. A combination of differential scanning calorimetry (DSC), polarisation optical microscopy (POM) and X-ray diffraction revealed that the chiral N-BTA derivatives with branched 3,7-dimethyloctanoyl chains were liquid crystalline and the mesophase was assigned as Colho. In contrast, N-BTA derivatives with linear tetradecanoyl or octanoyl chains lacked a mesophase and were obtained as crystalline compounds. Variable-temperature infrared spectroscopy showed the presence of threefold, intermolecular hydrogen bonding between neighbouring molecules in the mesophase of the chiral N-BTAs. In the crystalline state at room temperature a more complicated packing between the molecules was observed. Ultraviolet and circular dichroism spectroscopy on dilute solutions of N-BTAs revealed a cooperative self-assembly behaviour of the N-BTA molecules into supramolecular polymers with preferred helicity when chiral alkyl chains were present. Both the sergeants-and-soldiers as well as the majority-rules principles were operative in stacks of N-BTAs. In fact, the self-assembly of N-BTAs resembles closely that of their carbonyl (CO)-centred counterparts, with the exception that aggregation is weaker and amplification of chirality is less pronounced. The differences in the self-assembly of N- and CO-BTAs were analysed by density functional theory (DFT) calculations. These reveal a substantially lower interaction energy between the monomeric units in the supramolecular polymers of N-BTAs. The lower interaction energy is due to the higher energy penalty for rotation around the PhNH bond compared to the PhCO bond and the diminished magnitude of dipole,dipole interactions. Finally, we observed that mixed stacks are formed in dilute solution when mixing N-BTAs and CO BTAs. [source] Syntheses, Phase Behavior, Supramolecular Chirality, and Field-Effect Carrier Mobility of Asymmetrically End-Capped Mesogenic OligothiophenesCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2009Qingwei Meng Dr. Abstract Supramolecular chirality and liquid crystalline OFET: Achiral end-capped oligothiophenes can be tuned to exhibit supramolecular chirality with unique striped textures showing distinct circular dichroism signals as well as a highly ordered SmE phase that leads to high hole carrier mobility. A novel series of asymmetrically end-capped mesogenic oligothiophenes, with various oligothiophene core lengths, alkoxy tail lengths, and molecular polarities through introducing alkylsulfanyl or alkylsulfonyl functionalities as the terminal group, have been synthesized by palladium-catalyzed Suzuki cross-coupling and Kumada cross-coupling reactions as key steps. For the single end-capped oligothiophenes, CmO-Ar-OT(4)-H in which m=10, 12, 14, 16, and 18, all of these oligomers exhibited a broad temperature range of highly ordered smectic E and enantiotropic nematic phases, apart from the one with the longest octadecyloxy tail. For the double end-capped series C10O-Ar-OT(n)-R, R=Ph-SC6 or Ph-SO2C6 in which n=1, 2, 3, and 4, oligomers with more than one thiophene ring exhibited smectic A and smectic C phases, various crystal polymorphs and/or unusual low-temperature condensed phases. In the nonpolar, alkylsulfanylphenyl-substituted oligothiophene series, both the crystal/solid melting point and mesogenic clear point increased significantly with an increasing oligothiophene conjugation length. In the polar, alkylsulfonylphenyl-substituted oligothiophene series, all the oligomers showed increased melting points, but decreased mesogenic temperature intervals than those of their corresponding alkylsulfanyl counterparts. Remarkably, two different helical structures showing distinct striated textures or striped patterns were observed with a pitch of several to tens of micrometers under a polarized optical microscope upon cooling from their preceding fluidic smectic phases. The unusual twisted smectic layer structures in the thin solid films exhibiting distinct supramolecular chirality of both handednesses, revealed by circular dichroism measurements, were further confirmed by XRD analyses characterized by a sharp layer reflection together with its higher orders and diffuse wide-angle scatterings. In addition, initial studies showed that the highly ordered smectic phase of the single end-capped oligothiophenes can be utilized to improve field-effect charge mobility. C10O-Ar-OT(4)-H showed a hole mobility of 0.07,cm2,V,1,s,1 when deposited on octyltrichlorosilane-treated substrates at 140,°C and the on/off current ratios reached 5×105; on the other hand, its mobility was only 8×10,3,cm2,V,1,s,1 on the same substrate when deposited at room temperature. [source] Unique Properties of DNA Interstrand Cross-Links of Antitumor Oxaliplatin and the Effect of Chirality of the Carrier LigandCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2008Jana Kasparkova Dr. Abstract The different antitumor and other biological effects of the third-generation antitumor platinum drug oxaliplatin [(1R,2R -diamminocyclohexane)oxalatoplatinum(II)] in comparison with those of conventional cisplatin [cis -diamminedichloridoplatinum(II)] are often explained by the ability of oxaliplatin to form DNA adducts of different conformation and consequently to exhibit different cytotoxic effects. This work describes, for the first time, the structural and biochemical characteristics of the interstrand cross-links of oxaliplatin. We find that: 1),DNA bending, unwinding, thermal destabilization, and delocalization of the conformational alteration induced by the cross-link of oxaliplatin are greater than those observed with the cross-link of cisplatin; 2),the affinity of high-mobility-group proteins (which are known to mediate the antitumor activity of platinum complexes) for the interstrand cross-links of oxaliplatin is markedly lower than for those of cisplatin; and 3),the chirality at the carrier 1,2-diaminocyclohexane ligand can affect some important structural properties of the interstrand cross-links of cisplatin analogues. Thus, the information contained in the present work is also useful for a better understanding of how the stereochemistry of the carrier amine ligands of cisplatin analogues can modulate their anticancer and mutagenic properties. The significance of this study is also reinforced by the fact that, in general, interstrand cross-links formed by various compounds of biological significance result in greater cytotoxicity than is expected for monofunctional adducts or other intrastrand DNA lesions. Therefore, we suggest that the unique properties of the interstrand cross-links of oxaliplatin are at least partly responsible for this drug's unique antitumor effects. [source] | ||||||||||||||||||||||||||||||||||