Single‐Scan Selective Excitation of Individual NMR Signals in Overlapping Multiplets

Abstract

2D NMR is an immensely powerful structural tool but it is time‐consuming. Targeting individual chemical groups by selective excitation in a 1D experiment can give the information required far more quickly. A major problem, however, is that proton NMR spectra are often extensively overlapped, so that in practice only a minority of sites can be selectively excited. Here we overcome that problem using a fast, single‐scan method that allows selective excitation of the signals of a single proton multiplet even where it is severely overlapped by other multiplets. The advantages of the method are illustrated in a selective 1D NOESY experiment, the most efficient way to determine relative configuration unambiguously by NMR. The new approach presented here has the potential to broaden significantly the applicability of selective excitation and unlock its real potential for many other experiments.

Targeted Compound Selection with Increased Sensitivity in 13C-Enriched Biological and Environmental Samples Using 13C-DREAMTIME in Both High-Field and Low-Field NMR

“…To demonstrate simultaneous selection of multiple compounds, Figure c depicts the selection of eight amino acids: aspartic acid, glycine, tyrosine, tryptophan, threonine, leucine, lysine, and valine (frequencies targeted are listed in Supporting Information Section S2). Unlike other selective experiments, − 13 C-DREAMTIME has the unique ability to selectively and cleanly detect a suite of analytes, as demonstrated here. For further information on multiple selection, readers should refer to the extensive practical guide in the original publication .…”

“…Therefore, techniques are needed to help overcome the sensitivity and spectral overlap limitations of NMR spectroscopy and improve its effectiveness in environmental and biological analysis. Selective experiments, such as chemical shift selective filter (CSSF) 2,3 and GEMSTONE 4 hold great promise for the analysis of chemical mixtures. A highly complementary method termed 13 C-DREAMTIME is introduced here, ideal for studying ultra-complex systems with extensive spectral overlap.…”

Application of multiplet structure deconvolution to extract scalar coupling constants from 1D nuclear magnetic resonance spectra

“…We shall not discuss, here, the deconvolution of spectral line shapes but shall concentrate on the deconvolution of the effect of coupling interactions called "multiplet-structure deconvolution". Following developments in the time domain (Le Parco et al, 1992;Bothner-By and Dadok, 1987;Prost et al, 2006), the frequency domain became more popular to avoid the back-and-forth Fourier transformation. This branch of research started in the 1980s in the group of R. Freeman (del Río Portilla et al, 1994), continued in the 1990s in Geoffrey Bodenhausen's group (Huber and Bodenhausen, 1993a, b;Jeannerat, 2000;Jeannerat and Bodenhausen, 1999) and continued to resonate when the ACCA method (Cobas et al, 2005) was developed for Mestrelab's software Mnova.…”

Application of multiplet structure deconvolution to extract scalar coupling constants from 1D NMR spectra

“…It is therefore of fundamental importance to provide chemists with the most powerful tools to analyse multiplets in particular in the cases where the multiplet structure is too complex to be deciphered by visual inspection because of high degeneracy (complex structures such as "dqd"), partial overlap of multiplet structures or second-order effects. The measurement of scalar coupling constants has been the object of very intense academic work, either for direct application to 1D spectra (McIntyre and Freeman, 1992;del Río Portilla and Freeman, 1993) or involving the development of NMR pulses sequences producing spectra where coupling constants can be measured easily (Marquez et al, 2001) even in situations of extensive overlap (Prasch et al, 1998;Kiraly et al, 2020;Berger, 2018). The sad observation is that the impact of these developments is extremely limited because the broad community of chemists almost exclusively rely on basic 1D 1 H spectra to extract coupling constants.…”