Long-Range ¹H−¹⁵N Heteronuclear Shift Correlation at Natural Abundance

Abstract

Despite the inherently low sensitivity of (15)N NMR because of its low gyromagnetic ratio (gamma(N)) and its relatively low natural abundance (0.37%), this important nuclide still has useful potential as a structural probe even at natural abundance. Inverse-detected NMR methods coupled with major advances in NMR probe designs have made it possible to acquire long-range (1)H-(15)N heteronuclear shift correlation data on samples as small as a micromole overnight. Chemical shift referencing schemes for (15)N and the range of (15)N shifts are discussed, followed by a discussion of the currently available pulse sequences, pulse calibration, parametrization and processing of long-range (1)H-(15)N data, and the implications of probe selection. These topics are followed by a review of the applications contained in the literature that have utilized (1)H-(15)N heteronuclear shift correlation experiments at natural abundance, with emphasis placed on the observed long-range coupling pathways.

Long-Range1H-15N Heteronuclear Shift Correlation at Natural Abundance: a Tool To Study Benzothiazole Biodegradation by TwoRhodococcusStrains

“…Among the new sequencing methods available recently (24), the choice of the GHMBC experiment (20) was guided by the ease in setting up this kind of experiment and by its high distribution on most commercial spectrometers. In the scheme of the pulse program (for details, see reference 24) a variable delay is included between the two first 90°1 5 N pulses.…”

“…Other technical improvements were reached by using specific probes or new NMR sequences. More details are available in a recent and very interesting review (24) about the application of this technique to the determination of natural product structure, particularly of alkaloids. One-and twodimensional inverse 1 H- 15 N experiments have been used to detect 15 N-enriched metabolites, mainly amino acids in mammalian (21,28), insect (11,12), and plant (25) cells.…”

Benzothiazole Degradation by Rhodococcus pyridinovorans Strain PA: Evidence of a Catechol 1,2-Dioxygenase Activity

“…Various NMR techniques were used. (i) In situ 1 H NMR was performed directly with culture media at natural abundance and allowed biodegradation kinetics to be monitored; this approach was used previously to study microbial biodegradation of xenobiotic compounds (3, 5, 8-10, 13, 14, 29 (2,24,26).…”

Quindolinocryptotackieine: the elucidation of a novel indoloquinoline alkaloid structure through the use of computer‐assisted structure elucidation and 2D NMR

“…Better experimental access is available to long-range 1 19 Long-range 1 H-15 N 2D NMR experiments at natural abundance, which might also be of additional help in the assembly of substructural fragments and the elucidation of the structure, are also now possible and the subject of a recent review. 20,21 The second structure shown in Fig. 7 is assigned as the structure.…”