Bijvoet's method, which makes use of anomalous x-ray diffraction or dispersion, is the standard means directly determining absolute (stereochemical) configuration molecules, but it requires crystalline samples and often proves challenging in structures exclusively comprising light atoms. Herein, we demonstrate a mass spectrometry approach that images individual molecules gas phase by cold target recoil ion momentum spectroscopy after laser ionization-induced Coulomb explosion. This technique...

This review presents a comprehensive treatment of sulfoximine chemistry particularly emphasising synthetic developments and structural work after 1985. Following brief introduction, the structures properties sulfoximines metallated are discussed. The second section deals with preparation new methods. main part is concerned reactions sulfoximines. material in this organised based on reactivity pattern displayed by various Therefore they grouped roughly into three classes compounds. first...

Under the 2D NMR spectroscopic magnifying glass: The intermediacy of 1 in Pd-catalyzed allylic substitution was investigated and proven. Characterization this Pd0 complex, which is primarily formed catalytic cycle, shows that attack nucleophile malonate at double bond allyl ligand preferred trans to P atom.

Helically chiral polymers from achiral monomers containing N and P atoms have been shown to be ligands for transition metals such as Pd Rh. The Rh complex of the phosphane-containing polyisocyanate p(18- co -17) was an active albeit hardly enantioselective catalyst in asymmetric hydrogenation dehydro amino acid -acetamidocinnamic (15% enantiomeric excess). most obtained until now Pd-complexed polymethacrylate Pd-p12, which catalyzes allylic substitution reaction 1,3-diphenylprop-2-enyl...

No other sources of chirality except its helicity are present in the polymeric ligand shown, which was prepared by helix-sense-selective polymerization. Palladium complexes this catalyze allylic substitution reactions. The resulting asymmetric induction is a direct and sole consequence uniform ligand.

Orientation help: Valine-derived polyacetylenes are introduced as enantiomer-differentiating alignment media. The F2-coupled HSQC-type NMR spectra of both enantiomers isopinocampheol (IPC) display narrow line widths allowing for the precise extraction residual dipolar couplings (black contour plot: (+)-IPC in an isotropic phase, blue: (−)-IPC anisotropic and red: phase; J=coupling constant). Detailed facts importance to specialist readers published "Supporting Information". Such documents...

Abstract The reaction of cyclosporin A (CsA) with Lawesson 's reagent under different conditions yields various thiocyclosporins, in which carbonyl O‐atoms and/or the hydroxy O‐atom MeBmt residue are replaced by an S‐atom. position S‐atom is determined NMR spectroscopy, and conformations products studied spectroscopy X‐ray crystallography. Some thiocyclosporins show interesting conformational properties. Whereas one conformation strongly dominates for CsA CDCL 3 , two conformers B, a ratio...

Handy polymers: The lyotropic liquid-crystalline phases of helically chiral polyguanidines are proposed as new orienting media for organic compounds. enantiomers isopinocampheol (IPC) oriented in an enantiodifferentiating manner (see figure). difference orientation induced the two seems to be larger than one observed poly-γ-benzyl-L-glutamate (PBLG). Detailed facts importance specialist readers published "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset....

Insensitive towards inversion: Can residual dipolar couplings (RDCs) and other anisotropic NMR observables be used to determine absolute configuration? A critical assessment of recent approaches is provided the configuration from RDCs.

A series of systematically varied (eta3-1,3-dialkylallyl)palladium complexes (4S)-[2-(2-diphenylphosphanyl)phenyl]-4,5-dihydrooxazole (PHOX) ligands were characterized by X-ray crystal structure analysis and NMR spectroscopy. Complexes with identical substituents in the 1,3-positions allyl group can form eight stereoisomers. In solution four to six isomers observed their conformations assigned aid NOE experiments. The dynamic behavior was analyzed. addition, quantum-chemical calculations...

A study of dynamic nuclear polarization (DNP) in polyethylene glycol and related nonionic surfactants is presented. In these experiments, we found the surprising result that DNP enhanced 13C magic angle spinning (MAS) spectra display two sets resonances, one with broad sharp spectral features are 180° opposite phase. These indicate presence a direct transfer channel as expected for MAS second unexpected indirect channel. Plots enhancements function applied magnetic field resonances show...

Abstract A new method implemented into a computer program ( ConArch + ) has been developed and applied to demonstrate the successful implementation of residual dipolar couplings (RDCs) in distance geometry (DG) calculations for configurational assignment chiral compounds. Unlike established protocols, approach combines floating chirality (fc) 4D‐ 3D‐distance bounds driven dynamics (DDD) with structural information from RDCs. Thus, relative configurations compounds were generated only by...

Abstract 3D molecular structure determination is a challenge for organic compounds or natural products available in minute amounts. Proton/proton and proton/carbon correlations yield the constitution. J couplings NOEs oftentimes supported by one-bond 1 H, 13 C residual dipolar (RDCs) chemical shift anisotropies (RCSAs) provide relative configuration. However, these RDCs carbon RCSAs rely on 1% abundance of preventing their use only quantities few 10’s µgs. By contrast, H similar information...

Four pyridyl substituted helically chiral poly(methacrylate)s poly-1−poly-4 were oxidized with m-CPBA, yielding four N-oxide polymers poly-5−poly-8. Poly[(3-pyridyl N-oxide)dibenzosuberyl methacrylate] poly(3PyDBSMA-NO) poly-5 was found to be quantitatively and showed a stable helical conformation. It an active organocatalyst in the asymmetric allylation of benzaldehyde allyltrichlorosilane.

Lyotropic liquid crystalline phases of a phenylalanine‐based polyacetylene are introduced as new enantiodifferentiating alignment media. Based on the unusual temperature dependence quadrupolar splitting 2 H‐signal solvent (CDCl 3 ), three distinct states phase with different orientational properties can be identified. This offers opportunity to measure multiple data sets without changing sample. Unexpectedly, largest difference in orientation enantiomers isopinocampheol was found high domain...

Abstract In this work, the practical/analytical potential of an L‐valine‐derived polyacetylene (PLA) lyotropic liquid crystal (LLC) is examined to spectrally discriminate enantiomers (racemic mixture) or enantiotopic directions a large collection (23) (pro)chiral model compounds (from rigid flexible and polar apolar ones), thus covering various important aspects enantiomorphism. Experimental 2 H‐{ 1 H} (deuterated analytes at natural abundance level) 13 C‐{ NMR results are discussed in terms...

Residual dipolar couplings and other anisotropic NMR parameters are powerful tools for molecular structure elucidation when conventional techniques do not suffice. With current liquid crystalline preparations it is necessary to prepare two samples extract isotropic data from spectra derive the residual couplings. Here, we present preparation, measurement, interpretation of a novel biphasic phase where single sample can be used generate both data. First, introduce synthesis chiral polymer...

Orientierungshilfe: Valin-basierte Polyacetylene werden als enantiomerdifferenzierende Orientierungsmedien eingeführt. F2-gekoppelte HSQC-artige NMR-Spektren beider Enantiomere von Isopinocampheol (IPC) weisen schmale Linienbreiten auf, die eine präzise Ermittlung dipolarer Restkopplungen ermöglichen (schwarz: (+)-IPC in einer isotropen Phase, blau: (−)-IPC anisotropen rot: Phase). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents...

The application of metalated, enantiomerically pure acyclic and cyclic 2-alkenyl sulfoximines for the synthesis highly substituted aza(poly)cyclic ring systems is described. method relies on a one-pot combination reagent-controlled allyl transfer reaction to α- or β-amino aldehydes, followed by Michael-type cyclization intermediate vinyl generated in first step. sulfur-free target compounds are preferentially obtained samarium iodide treatment sulfonimidoyl heterocycles. In addition this...

Comparative quantification of the enantiodiscrimination capability four polymeric chiral lyotropic liquid crystals using natural abundance deuterium 2D-NMR spectroscopy.

Erstmals nachgewiesen und 2D‐NMR‐spektroskopisch unter die Lupe genommen wurde das Intermediat 1 der Pd‐katalysierten allylischen Substitution. Die Ergebnisse Charakterisierung dieses im Katalysecyclus primär gebildeten Pd 0 ‐Komplexes belegen, daß Angriff des Nucleophils Malonat an Doppelbindung Allylliganden bevorzugt auf trans ‐Seite bezüglich P‐Atoms stattfindet. magnified image

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination of conformation and relative configuration a small, rapidly tumbling molecule in solution by combined application NOESY restrained MD calculationsMichael Reggelin, Holger Hoffmann, Matthias Koeck, Dale F. MierkeCite this: J. Am. Chem. Soc. 1992, 114, 9, 3272–3277Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 April...