Homonuclear BIRD-decoupled spectra for measuring one-bond couplings with highest resolution: CLIP/CLAP-RESET and constant-time-CLIP/CLAP-RESET

Unambiguous spectral assignments in (1)H solution-state NMR are central, for accurate structural elucidation of complex molecules, which is often hampered by signal overlap, primarily because of scalar coupling multiplets, even at typical high magnetic fields. The recent advances in homodecoupling methods have shown powerful means of achieving high resolution pure-shift (1)H spectra in 1D and also in 2D J-correlated experiments, by effectively collapsing the multiplet structures. The present work extends these decoupling strategies to through-space correlation experiments as well and describes two new pure-shift ROESY pulse schemes with homodecoupling during acquisition, viz., homodecoupled broadband (HOBB)-ROESY and homodecoupled band-selective (HOBS)-ROESY. Furthermore, the ROESY blocks suppress the undesired interferences of TOCSY cross peaks and other offsets. Despite the reduced signal sensitivity and prolonged experimental times, the HOBB-ROESY is particularly useful for molecules that exhibit an extensive scalar coupling network spread over the entire (1)H chemical shift range, such as natural/synthetic organic molecules. On the other hand, the HOBS-ROESY is useful for molecules that exhibit well-separated chemical shift regions such as peptides (NH, Hα and side-chain protons). The HOBS-ROESY sensitivities are comparable with the conventional ROESY, thereby saves the experimental time significantly. The power of these pure-shift ROESY sequences is demonstrated for two different organic molecules, wherein complex conventional ROE cross peaks are greatly simplified with high resolution and sensitivity. The enhanced resolution allows deriving possibly more numbers of ROEs with better accuracy, thereby facilitating superior means of structural characterization of medium-size molecules.

Section: Introductionmentioning

confidence: 99%

Real‐time homonuclear broadband and band‐selective decoupled pure‐shift ROESY

Kakita

Jagadeesh

2014

“…An important practical application of the pure shift techniques is the determination of the magnitude and sign of scalar and residual dipolar coupling constants through the highly resolved and simplified pure shift spectra. [21,22,25,[48][49][50][51][52][53][54][55] Further promising applications are currently in their initial stage of development, such as the combination of pure shift with the dynamic nuclear polarization technique [56] or the use of pure shift spectra to carry out quantitative studies in metabolomics. [57] In the future, it could also be possible to explore the application of pure shift techniques to other nuclei (such as 19 F, 31 P or 2 H), in quality control processes, drug degradation studies and to monitor fast reactions, among others.…”

Section: Applicationmentioning

confidence: 99%

Pure shift ¹H NMR: what is next?

Castañar

2016

“…These issues become particularly apparent for pairs of diasterotopic protons, where bilinear rotation decoupling filtration fails because of the protons being attached to the same carbon and 2 D HH RDCs of large magnitude are often observed. Recently, some of the developments in the field of pure shift techniques were incorporated into these pulse sequences, giving much improved lineshapes and facilitating reliable RDC extraction, where the basic methods fail because of distorted lineshapes . Representative examples of these experiments in both isotropic and anisotropic media are shown in Figs and .…”

Section: Measurement Of Residual Dipolar Couplingsmentioning

confidence: 99%

Perspectives in the application of residual dipolar couplings in the structure elucidation of weakly aligned small molecules

Schmidts

2016

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