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40 results on '"Cheshkov, Dmitry"'

1. Total lineshape analysis of {\alpha}-tetrahydrofuroic acid $^{1}$H NMR spectra

Author

Nichugovskiy, Artemiy I. and Cheshkov, Dmitry A.

Subjects
Physics - Chemical Physics
Abstract

The 1H NMR spectra of L-proline oxygen analogous, alpha-tetrahydrofuroic acid, 7-spins nonsymmetric spin system with strongly pronounced non-first order effects were analyzed by ANATOLIA total lineshape fitting. A close agreement of theoretical and experimental spectra (with R-Factor values bellow 5%) was achieved and accurate values of coupling constant were obtained. The carboxylic substituent disrupts tetrahydrofuran symmetry and allows to unambiguously determine the typical values of geminal coupling constants in oxygen-containing saturated five-membered ring systems.

Published
2022

2. Photochemically induced dynamic nuclear polarization of heteronuclear singlet order

Author

Sheberstov, Kirill F., Chuchkova, Liubov, Hu, Yinan, Zhukov, Ivan V., Kiryutin, Alexey S., Eshtukov, Artur V., Cheshkov, Dmitry A., Barskiy, Danila A., Blanchard, John W., Budker, Dmitry, Ivanov, Konstantin L., and Yurkovskaya, Alexandra V.

Subjects
Physics - Chemical Physics
Abstract

Photochemically induced dynamic nuclear polarization (photo-CIDNP) is a method to hyperpolarize nuclear spins using light. In most cases, CIDNP experiments are performed at a high magnetic field and the sample is irradiated by the light inside a nuclear magnetic resonance (NMR) spectrometer. Here we demonstrate photo-CIDNP hyperpolarization generated in the Earth magnetic field and under zero- to ultralow field (ZULF) conditions. Irradiating a sample for several seconds with inexpensive light-emitting diodes produces a strong hyperpolarization of 1H and 13C nuclear spins enhancing the NMR signals several hundred times. The hyperpolarized spin states at the Earth field and in ZULF are different. In the latter case, the state corresponds to the singlet order between scalar-coupled 1H-13C nuclear spins. This state has a longer lifetime than the state hyperpolarized at Earth field. The method is simple and cost-efficient and should be applicable to many molecular systems known to exhibit photo-CIDNP, including amino acids and nucleotides.

Published
2021

4. Congestion effect of an annulated tetracyclic thiophene-containing fragment on 18-crown-6 ether: manifestation in complex formation in solution and membrane transfer properties.

Author

Khoroshutin, Andrey, Martynov, Leonid, Yaltseva, Polina, Kostenko, Evita, Cheshkov, Dmitry, Botezatu, Anatoliy, Moiseeva, Anna, Fedorov, Yuri, and Fedorova, Olga

Abstract

Two novel macrocyclic compounds with a crown ether moiety annulated to a tetracyclic thiophene-containing aromatic fragment were synthesized by the Mallory–Katz photocyclization reaction from a single stilbene precursor. These compounds were produced by cyclization of its two conformers and differed in the degree of steric hindrance exerted by the tetracyclic fragment on the crown ether. Their complexation with ammonium and barium perchlorates was studied both in solution by NMR, UV-vis, and fluorescence spectroscopy, and in PVC membrane by crown ether-facilitated ion transfer between the aqueous and membrane phases. In solution, the congestion of the crown ether is manifested by different responses of the spectra of the two isomers to the addition of salts. Also, the sterically hindered isomer exhibits weaker binding to the studied ions than the unhindered one. Besides, congested isomer exhibit larger decrease of the diffusion coefficient on complexation. In PVC membrane, the observed binding constants are higher, although the difference between the congested and uncongested isomers is less pronounced. Analysis of possible conformations by the MMFF94 force field and DFT calculations was made to account for features of NMR spectral changes upon complexation. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Total lineshape analysis of α-tetrahydrofuroic acid $^{1}$H NMR spectra

Author

Nichugovskiy, Artemiy I. and Cheshkov, Dmitry A.

Subjects
Chemical Physics (physics.chem-ph), FOS: Physical sciences
Abstract

The 1H NMR spectra of L-proline oxygen analogous, alpha-tetrahydrofuroic acid, 7-spins nonsymmetric spin system with strongly pronounced non-first order effects were analyzed by ANATOLIA total lineshape fitting. A close agreement of theoretical and experimental spectra (with R-Factor values bellow 5%) was achieved and accurate values of coupling constant were obtained. The carboxylic substituent disrupts tetrahydrofuran symmetry and allows to unambiguously determine the typical values of geminal coupling constants in oxygen-containing saturated five-membered ring systems.

Published
2022
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14. Photochemically Induced Dynamic Nuclear Polarization of Heteronuclear Singlet Order

Author

Sheberstov, Kirill F., primary, Chuchkova, Liubov, additional, Hu, Yinan, additional, Zhukov, Ivan V., additional, Kiryutin, Alexey S., additional, Eshtukov, Artur V., additional, Cheshkov, Dmitry A., additional, Barskiy, Danila A., additional, Blanchard, John W., additional, Budker, Dmitry, additional, Ivanov, Konstantin L., additional, and Yurkovskaya, Alexandra V., additional

Published
2021
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37. Furan RingOpeningIndole RingClosure: Pictet–SpenglerLike Reaction of 2oAminophenylfurans with Aldehydes

Author

Butin, Alexander V., Uchuskin, Maxim G., Pilipenko, Arkady S., Tsiunchik, Fatima A., Cheshkov, Dmitry A., and Trushkov, Igor V.

Abstract

A new simple approach to 32acylvinyl2heteroarylindoles has been developed. The method is based on the acidcatalysed interaction of 22aminophenylfurans withheteroaromatic aldehydes. The reactions proceed under very mild conditions and lead to indoles containing a reactive α,βunsaturated ketone moiety, which is suitable for further transformations, in moderate to good yields.

Published
2010
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39. Copper(I)-Catalyzed Cycloaddition of Azides to Multiple Alkynes: A Selectivity Study Using a Calixarene Framework.

Author

Gorbunov A, Cheshkov D, Kovalev V, and Vatsouro I

Abstract

Copper(I)-catalyzed addition of limited amounts of azides to multiple alkynes, which led to statistical mixtures of triazole/acetylene derivatives or, in other cases, resulted in preferred formation of multiple triazoles, was studied at pre-organizable calixarene platforms bearing up to four propargyl groups. Depending on calixarene structures and reaction conditions, the unprecedented specific or selective formation of exhaustively triazolated calixarenes or a complete loss of the selectivity were observed. Both autocatalytic copper activation and a local copper(I) concentration increase due to copper-triazole complexation were thoroughly studied as the most expected reasons for the selectivity and both were disproved. Mixed triazolated/propargylated calixarenes and their copper(I) complexes proved not to be involved in the cascade-like process that was modeled to be driven by an intramolecular transfer of two copper(I) ions from a just-formed binuclear copper intermediate to the adjacent acetylene unit., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2015
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40. Calix[4]tubes: an approach to functionalization.

Author

Puchnin K, Zaikin P, Cheshkov D, Vatsouro I, and Kovalev V

Subjects
Calixarenes chemical synthesis, Esters, Magnetic Resonance Spectroscopy, Models, Molecular, Adamantane analogs & derivatives, Calixarenes chemistry, Tosyl Compounds chemistry, Urea analogs & derivatives
Abstract

Adamantylcalix[4]arenes decorated with ester groups and calix[4]arene tetratosylates were used to prepare a series of calix[4]tubes bearing 3-methoxycarbonyl- and 3-methoxycarbonylmethyl-1-adamantyl units (up to eight) in good yield. These compounds were subjected to further chemical transformations giving a wide set of novel ester-, acid-, hydroxy-, amine-, and urea-functionalized calix[4]tubes. Introduction of urea groups into the calixtube core led not only to anion-targeted receptors, but also provided heteroditopic behavior of the hosts, which enriches the well-established potassium-uptake ability of calix[4]tubes., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2012
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