Abstract After the huge impact that residual dipolar couplings (RDCs) have had on structure determination of biological macromolecules by NMR spectroscopy, their utility in small/medium‐sized organic compounds is more and recognised. This microreview will provide a short overview how to introduce anisotropic environment necessary measure RDCs, corresponding measurement methods applications for relative configurations assignment diastereotopic moieties. Their application rigid be described,...

Photocontrol of a piperidine's Brønsted basicity was achieved by incorporation bulky azobenzene group and could be translated into pronounced reactivity differences between ON- OFF-states in general base catalysis. This enabled successful photomodulation the catalyst's activity nitroaldol reaction (Henry reaction). A modular synthetic route to photoswitchable catalysts developed allowed for preparation characterization three azobenzene-derived bases as well one stilbene-derived base....

Abstract Moisture-responsive materials are gaining greater interest for their potentially wide applications and the readily access to moisture. In this study, we show fabrication of moisture-responsive, self-standing films using sustainable cellulose as starting material. Cellulose was modified by stearoyl moieties at first, leading esters (CSEs) with diverse degrees substitution (DSs). The CSE a low DS 0.3 (CSE ) exhibited moisture-responsive properties, while CSEs higher DSs 1.3 or 3 not....

Peptides and proteins, that have the tendency to form aggregates, are often discussed in context of Alz-heimer’s, Huntington’s, or Parkinson’s disease. However, studying aggregation processes is inherently challenging due diversity aggregate size geometry lack control over process space time. Here, we present a small, synthetic peptide, for which can be controlled reversibly with light within seconds. Specifically, by incorporating photoswitchable unnatural amino acids into sequence...

Residual dipolar couplings were successfully used to distinguish between the two diastereotopic protons on C-20 of strychnine dissolved in an organic liquid crystal (PBLG/CDCl(3)). The results presented here strongly suggest that this method will be help structure determination, making determination relative stereochemistry absence NOE data possible.

The concept of using residual dipolar couplings (RDCs) for the structure determination organic molecules is applied to simultaneous assignment all diastereotopic protons in strychnine. To use this important NMR parameter molecule has be aligned magnetic field. Here we present a new alignment medium substrates. optimization properties mixtures poly-γ-ethyl-l-glutamate (PELG) and CDCl3 are described PELG at different concentrations evaluated. A comparison with poly-γ-benzyl-l-glutamate (PBLG)...

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...

Abstract A molecule that is introduced into a liquid crystal or alignment medium forfeits its isotropic tumbling motion. The resulting partial leads to observable anisotropic interactions, dipolar couplings being one. To control the degree of experiences essential retain quality high‐resolution solution‐state spectra. An overview media given. problems associated with very large residual (RDCs) are pointed out, and means reduce for strychnine in substituted polyglutamate crystals described....

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 Noncovalent interactions, especially hydrogen‐bonding interactions as well electrostatic forces, confined within one macromolecule are the key to designing foldamers that adopt well‐defined conformations in solution. In context of significant recent activities area triazole‐connected foldamers, so‐called clickamers, we present a fundamental study compares various model compounds bear adjacent N‐, O‐, or F‐heteroatom substituents. The interplay attractive and repulsive leads...

Abstract This Concept article highlights the development of a novel analytical tool, LED‐NMR (a combination in situ light illumination using light‐emitting diode and NMR spectroscopy) its variant UVNMR (LED‐NMR coupled with UV/Vis absorption spectroscopy), as well their applications mechanistic investigation light‐induced transformations. The utility these new tools has been demonstrated by providing rich kinetic structural data reaction species offering insights into photochemical...

syn- or anti-pathy? Determination of the relative configuration α-methylene-γ-butyrolactone 1 failed by conventional NMR methods, because structures in conformational space both diastereoisomers exist that fulfill restraints from NOE and 3J coupling data equally well. Homo- heteronuclear residual dipolar couplings were measured which indicate is trans configured.

Abstract Residual dipolar couplings (RDCs) have recently become increasingly important in organic structure determination due to their unique information content. One main limitation for the use of RDCs compounds, however, is that compound question needs be oriented with respect magnetic field order measure RDCs. So far, there are very few possibilities modulating induced degree orientation. The situation even worse when chiral orienting media considered, which could allow absolute...

Estimates of intramolecular distances are essential for structure determination (see figure). For medium-sized molecules, ROESY NMR spectroscopy is the method choice obtaining distances. However, integration cross-peaks problematic, owing to offset dependence integrals and/or TOCSY artefacts. We here present EASY (Efficient Adiabatic SYmmetrized ROESY), which yields reliable without a sample-specific setup.

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...

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.

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

Abstract The COSY experiment is an essential homonuclear 2D NMR for the assignment of resonances. Its multiplet line shape, however, often overly complicated, potentially leads to signal intensity losses, and responsible long minimum overall acquisition times. Herein, we present CLIP‐COSY, a COSY‐type yielding clean in‐phase peaks. It can be recorded within few minutes benefits from enhanced intensities most cross‐peaks. In combination with non‐uniform sampling, times further reduced,...

The aerobic dehydrogenative lactonization of alkenoic acids facilitated by a cooperative nonmetallic catalyst pair is reported. title procedure relies on the adjusted interplay photoredox and selenium-π-acid catalyst, which allows for regiocontrolled construction five- six-membered lactone rings in yields up to 96%. Notable features this method are pronounced efficiency practicality, good functional group tolerance, high sustainability, since ambient air visible light adequate clean...

A strategy towards photochromic SI-ROMP homopolymers based on spiropyran and spirooxazine in mesopores is presented photochromism systematically investigated using UV-VIS spectroscopy NMR.

We report broadband proton-decoupled CLIP/CLAP-HSQC experiments for the accurate determination of one-bond heteronuclear couplings and, by extension, reliable measurement small residual dipolar coupling constants. The combination an isotope-selective BIRD((d)) filter module with a non-selective (1)H inversion pulse is employed to refocus proton-proton evolution prior acquisition brief chunks free induction decay that are subsequently assembled reconstruct fully-decoupled signal evolution. As...

<italic>In situ</italic> irradiation NMR spectroscopy allows for the distinction and quantification of different photoisomers.