The determination of 17O NMR parameters of hydroxyl oxygen: a combined deuteration and DOR approach (original) (raw)
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Tetrahedron Letters, 2004
The hypothesis and the conclusions of previous 17 O NMR studies on the detection of both oxygens of the carboxylic group of Boc-[ 17 O]Tyr(2,6-diClBzl)-OH in DMSO-d 6 solution (V. Tsikaris et al., Tetrahedron Lett. 2000, 41, 8651) are reconsidered. The appearance of two discrete resonances at 340 and 175 ppm of this protected amino acid is not now attributed: (a) to the reduction of the intramolecular conformational exchange rate, due to the effect of intramolecular hydrogen bonding of the hydroxy part of the carboxyl with the carbonyl oxygen of the Boc-group, and (b) to the effect of solvent viscosity, suggested in the mentioned study. The cause of this phenomenon is now attributed to a strong hydrogen bonding of the polar proton acceptor solvent DMSO with the carboxy group, which effectively reduces the proton exchange rate, thus becoming slow on the 17 O NMR time scale. Ó 2004 Elsevier Ltd. All rights reserved. 17 O NMR spectroscopy provides a powerful and sensitive tool for studying intra-and intermolecular hydrogen bonding effects both in solution and in the solid state. 1-4 Since the oxygen atom is one of the most important atoms constituting hydrogen-bonding structures, 17 O NMR might provide novel and complementary information not readily available from other methods.
A review of oxygen-17 solid-state NMR of organic materials—towards biological applications
2004
17O solid state NMR of organic materials is developing rapidly. This article provides a snapshot of the current state of development of this field. The NMR techniques and enrichment protocols that are driving this progress are outlined. The 17O parameters derived from solid-state NMR experiments are summarized and the structural sensitivity of the approach to effects such as hydrogen bonding highlighted. The prospects and challenges for 17O solid-state NMR of biomolecules are discussed.
I. 1 A Review of Oxygen-17 Solid State NMR of Organic Materials
∎ ABSTRACT 17O solid state NMR of organic materials is developing rapidly. This article provides a snapshot of the current state of development of this field. The NMR techniques and enrichment protocols that are driving this progress are outlined. The 17O parameters derived from solid state NMR experiments are summarized and the structural sensitivity of the approach to effects such as hydrogen bonding highlighted. The prospects and challenges for 17O solid state
An Investigation of the 17 O NMR Chemical Shifts in Oxiranes Using Magnetically Corrected Basis Sets
The Journal of Physical Chemistry A, 2002
The results of theoretical and experimental investigation of 17 O NMR chemical shifts for a number of epoxidic compounds are reported. The calculations were performed for the MP2/6-311G(d) level reference geometries using the GIAO and CSGT methods within the coupled Hartree-Fock perturbation theory. Various basis sets were applied in calculations of the chemical shifts. The performance of recently developed magnetically consistent basis sets and their advantages over the standard ones are discussed. The obtained results allow one to assign NMR signals for epoxides for which experimental data were obtained for the mixtures of stereoisomers.
Probing O–H Bonding through Proton Detected 1H–17O Double Resonance Solid-State NMR Spectroscopy
Journal of the American Chemical Society, 2018
The ubiquity of oxygen in organic, inorganic, and biological systems has stimulated the application and development of 17O solid-state NMR spectroscopy as a probe of molecular structure and dynamics. Unfortunately, 17O solid-state NMR experiments are often hindered by the combination of broad NMR signals and low sensitivity. Here, it is demonstrated that fast MAS and proton detection with the D-RINEPT pulse sequence can be generally applied to enhance the sensitivity and resolution of 17O solid-state NMR experiments. Complete 2D 17O→1H D-RINEPT correlation NMR spectra were typically obtained in fewer than 10 hours from less than 10 milligrams of material, with low to moderate 17O enrichment (less than 20%). 2D 1H-17O correlation solid-state NMR spectra allow overlapping oxygen sites to be resolved on the basis of proton chemical shifts or by varying the mixing time used for 1H-17O magnetization transfer. In addition, J-resolved or separated local field (SLF) blocks can be incorporated into the D-RINEPT pulse sequence to allow direct measurement of one-bond 1H-17O scalar coupling constants (1JOH) or 1H-17O dipolar couplings (DOH), respectively; the latter of which can be used to infer 1H-17O bond lengths. 1JOH and DOH calculated from planewave density functional theory (DFT) show very good agreement with experimental values. Therefore, the 2D 1H-17O correlation experiments, 1H-17O scalar and dipolar couplings, and planewave DFT calculations provide a method to precisely determine proton positions relative to oxygen atoms. This capability opens new opportunities to probe interactions between oxygen and hydrogen in a variety of chemical systems. Disciplines
Physical chemistry chemical physics : PCCP, 2011
Monosodium L-glutamate monohydrate, a multiple oxygen site (eight) compound, is used to demonstrate that a combination of high-resolution solid-state NMR spectroscopic techniques opens up new possibilities for (17)O as a nuclear probe of biomolecules. Eight oxygen sites have been resolved by double rotation (DOR) and multiple quantum (MQ) NMR experiments, despite the (17)O chemical shifts lying within a narrow shift range of <50 ppm. (17)O DOR NMR not only provides high sensitivity and spectral resolution, but also allows a complete set of the NMR parameters (chemical shift anisotropy and electric-field gradient) to be determined from the DOR spinning-sideband manifold. These (17)O NMR parameters provide an important multi-parameter comparison with the results from the quantum chemical NMR calculations, and enable unambiguous oxygen-site assignment and allow the hydrogen positions to be refined in the crystal lattice. The difference in sensitivity between DOR and MQ NMR experimen...
Determination of NMR interaction parameters from double rotation NMR
Journal of Magnetic Resonance, 2007
It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The 17 O nuclei in isotopically enriched L-alanine and OPPh 3 are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In L-alanine the oxygen chemical shift span is 455 ± 20 ppm and 350 ± 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of ±5-10°. For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V 33 and d 33 ) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh 3 the principal axis of the 17 O EFG is found to be close to the O-P bond, and the 17 O-31 P one-bond J coupling ( 1 J OP = 161 ± 2 Hz) is determined to a much higher accuracy than previously.
Magnetic Resonance in Chemistry, 1999
The 17 O chemical shifts of simple aliphatic ethers were studied, and the additivity substituent increments for carbon atoms in the alkyl groups were determined. The additivity parameters were used to establish a linear correlation with experimental data for a series of aliphatic ethers, alcohols, vinyl ethers, trichloroacetyl vinyl ethers, alkyl phenyl ethers, alkyl formates, alkyl acetates and alkyl trichloroacetates. The use of correlation to estimate the 17 O chemical shifts allows the calculation of data with an accuracy better than š2.5 ppm.