Stereochemical behavior of 77 Se‐ 1 H spin‐spin coupling constants in pyrazolyl‐1,3‐diselenanes and 1,2‐diselenolane

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This is the first one of the three closely interrelated reviews to be published in Magnetic Resonance in Chemistry dealing with accordingly theoretical background, chemical applications, and biochemical studies of and by means of computational 1H NMR. Presented in the first part of the review is a general outline of the modern theoretical methods and accuracy factors of computational 1H NMR involving locally dense basis set schemes, solvent effects, vibrational corrections, and relativistic effects performed at the density functional theory and/or nonempirical levels. This review is dedicated to Prof. Stephan Sauer in view of his invaluable contribution to the field of computational nuclear magnetic resonance.

Section: Theoretical Methods and Accuracy Factorsmentioning

confidence: 99%

Computational ¹H NMR: Part 1. Theoretical background

Krivdin

2019

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“…There seems to be a tendency for the J value to follow the dihedral angle. It has been reported that 2 J (Se, H) is strongly dependent on the orientation of the selenium lone pair and 3 J (Se, H) follows classical Karplus‐type equation from experimental and theoretical approaches . 2 J (Se, C) have not been studied intensively and little is known about 3 J (Se, C) values .…”

Section: Resultsmentioning

confidence: 85%

“…The spin coupling constants of the seleno‐carbohydrates used in this study allow the following observations: J ( 77 Se, 13 C) value is explained by the hybrid orbital state, and the surrounding electron density seems to affect the value. 2 J ( 77 Se, 1 H) are greatly influenced by the dihedral angle formed with the selenium lone pair . Information on 2 J ( 77 Se, 13 C) is lacking thus preventing general conclusions. 3 J ( 77 Se, 1 H) values are for the most part explained by the Karplus relation . However, there are exceptions.…”

Section: Resultsmentioning

confidence: 99%

“…Our group is expanding the chemical synthesis of seleno sugars and oligosaccharides for applications in structural biology . Useful information on the conformational properties of seleno‐carbohydrates can be obtained from spin coupling constants such as 2‐3 J ( 77 Se, 1 H) . Extension to 1‐3 J ( 77 Se, 13 C) requires 1 H, 13 C, 77 Se triple resonance experiments, and J (Se, Se) and J (Se, C) in the octahedral clusters are possible .…”

Section: Introductionmentioning

confidence: 99%

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J(⁷⁷Se,¹H) and J(⁷⁷Se,¹³C) couplings of seleno‐carbohydrates obtained by ⁷⁷Se satellite 1D ¹³C spectroscopy and ⁷⁷Se selective HR‐HMBC spectroscopy

Uzawa

Shimabukuro

Suzuki

et al. 2018

Seleno-carbohydrates are those in which the oxygen of the glycosidic bond or the hydroxyl group is artificially replaced with selenium. This substitution changes H and C chemical shifts and produces spin coupling constants involving Se. Coupling constants, such as J( Se, H), are likely to be useful for conformational analyses of glycans because such couplings are never observed in natural glycans. Several papers have discussed the relationship between J( Se, H) and conformation; however, only few reports describe J( Se, C), which could also be useful. Here, we obtain Se coupling constants of seleno-carbohydrates from Se-selective HR-HMBC and Se satellites in 1D C spectra and examine their conformations using the Newman projection scheme.

“…Experimental measurements of 2 J (Se,H) are performed using the low‐power CPMG‐HSQMBC technique, as described in our previous publications, whereas all calculations of 77 Se‐ 1 H couplings are carried out within a general second order polarization propagator approach (SOPPA), which recently has been extensively used for the high‐level calculations of different types of spin‐spin coupling constants – in a large number of saturated carbocycles, nitrogen‐containing heterocycles, functional derivatives of aldehydes and ketones, cyclic and open‐chain nitrogen‐containing compounds, fluorobenzenes, organic phosphines and phosphine chalcogenides . In particular, 77 Se‐ 1 H couplings were calculated in very good agreement with experiment in selanylalkenes, as well as in five‐membered and six‐membered selenium‐containing heterocycles – selenophenes, diselenanes and diselenolanes, derivatives of thiaselenetane, selenasilole, thiaselenole, thiaselenolane and dihydrothiaselenine, as well as in three representative selenoglycosides . a…”

Section: Introductionmentioning

confidence: 99%

Resonance assignments of diastereotopic CH₂ protons in the anomeric side chain of selenoglycosides by means of ²J(Se,H) spin‐spin coupling constants

Rusakov

Krivdin

Kumar

et al. 2012

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Unambiguous resonance assignments of diastereotopic CH(2) protons in the anomeric side chain of nine alkyl- and aralkylselenoglycosides have been carried out on the basis of experimental CPMG-HSQMBC measurements and theoretical second order polarization propagator approach (SOPPA) calculations of geminal (77) Se-(1) H spin-spin coupling constants involving diastereotopic pro-R and pro-S protons. Theoretical conformational analyses have been performed at the MP2/6-311G** level. The conformational space of each of the selenoglycosides under study could be adequately described as a mixture of six interconverting conformers with the molar fractions depending on the nature of the side chain substituent at the selenium atom. The good agreement observed between measured and the weighted conformational averaged values of the calculated coupling constants provides a basis for reliable diastereotopic assignments in this type of carbohydrate structures.