The electron-donating properties of eighteen N-heterocyclic carbenes (N,N'-bis(2,6-dimethylphenyl)imidazol)-2-ylidene and the respective dihydro ligands) with 4,4'-R substituted aryl rings (4,4'-R = NEt2, OMe, Me, H, SMe, F, Cl, Br, I) in Grubbs II complexes were studied using electrochemical techniques. nature 4-R substituent has a strong influence on RuII/III redox potentials ranging between DeltaE1/2= +0.196 +0.532 V. Three unsymmetrical not equal to 4-R' also synthesized. Dynamic NMR...

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 This perspective article aims to review the general methodology in application of residual dipolar couplings (RDCs) structure elucidation small molecules and give author's view on challenges for future applications. Recent improvements availability alignment media, new pulse sequences measurement analysis software have garnered widespread interest technique. However, further generalization is needed order make RDC into a truly “routine” method. Copyright © 2016 John Wiley & Sons, Ltd.

Mission possible! The motional averaging of NMR spectroscopic data complicates the determination conformation and relative configuration in flexible organic molecules. Two alternative routes are discussed for treatment conformational equilibrium a moderately compound (see superposition two conformers butyrolactone studied) when residual dipolar couplings used. Detailed facts importance to specialist readers published as "Supporting Information". Such documents peer-reviewed, but not...

Full suppression of proton–proton couplings in pure shift HSQC spectra simplifies their analysis, as demonstrated for high precision RDC measurements.

We report on a detailed NMR spectroscopic study of the catalyst-substrate interaction highly enantioselective oligopeptide catalyst that is used for kinetic resolution trans-cycloalkane-1,2-diols via monoacylation. The extraordinary selectivity has been rationalized by molecular dynamics as well density functional theory (DFT) computations. Herein we describe conformational analysis organocatalyst studied combination nuclear Overhauser effect (NOE) and residual dipolar coupling (RDC)-based...

Abstract We determined the ensemble of conformations and therelative configuration dibromopalau'amine by using NMR parameters such as 3 J couplings, ROEs residual dipolar couplings. Based on electronic circular dichroism (ECD) optical rotatory dispersion (ORD) spectra were calculated DFT compared to experiment. By this method absolute natural (–)‐dibromopalau'amine was 6 S ,10 R ,11 ,12 ,16 ,17 ,18 ,20 .

The hygrophorones, a class of cyclopentenones isolated from fruiting bodies the genus Hygrophorus (basidiomycetes), show promising antifungal activity. While constitution 4,6-diacetylhygrophorone A12 (3) and relative configuration stereogenic centers in cyclopentenone ring were elucidated using standard NMR MS techniques, exocyclic center could not be assigned. By introducing sample 3 into an alignment medium measuring anisotropic parameters, namely, residual dipolar couplings, we able to...

The orientational properties of the two enantiomers an example compound, namely isopinocampheol [(+)- and (-)-IPC] in a liquid crystalline phase, Poly-gamma-benzyl-L/D-glutamate (PBLG/PBDG) with organic cosolvent CDCl(3), were investigated. interactions can be either enantiomorphous, leading to equal orientations residual dipolar couplings (RDCs), or diastereomorphous, different RDCs. difference between diastereomorphous was determined rather small (5 degrees Euler angle beta). Furthermore,...

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...

Lyotropic liquid crystalline (LLC) phases of polyglutamic acid derivatives, such as poly-γ-benzyl-l-glutamate, are suitable alignment media for organic structure elucidation by NMR spectroscopy. Their helical is responsible enantiodiscrimination. As part our ongoing investigations concerning the mechanism(s) these systems, we considered whether an additional chiral center in side chain could improve enantiodiscrimination relative to polymer with achiral chain. Therefore, diastereoisomers...

Stimuli responsive compounds and materials are of high interest in synthetic chemistry science, with light being the most intriguing stimulus due to possibility remote control physicochemical properties a molecule or material. There is constant quest design photoswitches improved switching efficiency especially diarylethene-type switches promise photo cyclization quantum yields up unity. However, only limited attention has been paid towards influence solution conformation on efficiency....

Poly(aspartic acid esters) are known to form either right-or left-handed α-helices depending on the ester group in side chain, solvent and/or temperature. Polyphenethyl-l-aspartates (PPLA) exhibit a helix reversal from right- with increasing We have recently reported application of polyphenethylaspartates as helically chiral alignment media. The thermoresponsivity observed for these polymers offers possibility measure different orientations analytes before and after medium at 373 K. Herein...

Mission possible! Die Bewegungsmittelung NMR-spektroskopischer Daten erschwert die Bestimmung der Konformation und relativen Konfiguration flexibler organischer Moleküle. Zwei Ansätze zur Behandlung des Konformationsgleichgewichts einer mäßig flexiblen Verbindung (siehe Überlagerung beiden Konformere untersuchten Butyrolactons) mithilfe dipolarer Restkopplungen werden diskutiert. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents...

We report a comprehensive study on novel, highly efficient, and biodegradable hybrid molecular transporters. To this end, we designed series of cell-penetrating, cube-octameric silsesquioxanes (COSS), investigated cellular uptake by confocal microscopy flow cytometry. A COSS with dense spatial arrangement guanidinium groups displayed fast kinetics cell permeation at nanomolar concentrations in living HeLa cells. Efficient was also observed bacteria, yeasts, archaea. The COSS-based carrier...

Residual dipolar couplings (RDCs) become increasingly important as additional NMR parameters in the structure elucidation of organic compounds but are usually used fitting procedures to discriminate between (computed) structures that accordance with RDCs and others can be ruled out. Thus, determination configurations requires prior structural information. The direct use restraints construct based on has only recently begun also compounds. No protocol been published though uses vector...

NMR techniques incorporating pure shift methods to improve signal resolution have recently attracted much attention, owing their potential use in studies of increasingly complex molecular systems. Extraction frequencies from these simplified spectra enables easier structure determination, but only a few the presented provide structural parameters derived integral measurements. In particular, for quantification nuclear Overhauser effect (NOE) it is highly desirable utilize where overlap...

Residual dipolar couplings (RDCs) contain information on the relative arrangement and dynamics of internuclear spin vectors in chemical compounds. Classically, RDC data is analyzed by fitting to structure models, while model-free approaches (MFA) directly relate RDCs corresponding vectors. The recently introduced software TITANIA implements MFA extracts parameters from facilitate de novo refinement for small organic Encouraged our previous results simulated data, we herein focus...

Inherently chiral compounds, such as calixarenes, are due to a nonplanar three-dimensional (3D) structure. Determining their conformation is essential understand properties, with nuclear magnetic resonance (NMR) spectroscopy being one applicable method. Using alignment media measure residual dipolar couplings (RDCs) obtain structural information advantageous when classical NMR parameters like the Overhauser effect (NOE) or

Abstract Wir stellen eine umfassende NMR‐spektroskopische Untersuchung der Katalysator‐Substrat‐Wechselwirkungen eines hochselektiven Oligopeptid‐Katalysators vor, welcher für die kinetische Racematspaltung von trans‐Cycloalkan‐1,2‐diolen via Monoacylierung verwendet wird. Die außerordentliche Selektivität wurde basierend auf Molekulardynamik‐Simulationen sowie DFT‐Rechnungen erklärt. In dieser Arbeit beschreiben wir Konformationsanalyse des Organokatalysators durch Kombination...

Residual dipolar couplings (RDCs) are amongst the most powerful NMR parameters for organic structure elucidation. In order to maximize their effectiveness in increasingly complex cases such as flexible compounds, a maximum of RDCs between nuclei sampling large distribution orientations is needed, including sign information. For this, easily accessible one-bond 1 H-13 C alone often fall short. Long-range H-1 H both abundant and typically sample highly complementary orientations, but accessing...

There has been much debate about the σ‐donor and π‐acceptor properties of N ‐heterocyclic carbenes (NHCs). While a lot synthetic modifications have performed with goal optimizing catalyst to tune reactivity in various transformations (e.g. metathesis), direct methods characterize are still few. We believe that dynamic NMR spectroscopy can improve understanding this aspect. Thus, we investigated intramolecular dynamics metathesis precatalysts bearing two NHCs. chose four systems one identical...