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Туров, А. В.; Bondarenko, S. P.; Tkachuk, A. A.; Khilya, V. P.

doi:10.1023/a:1010523603932

Cited by 3 publications

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“…In the recent years, new fields of application of LSR were found, e.g., enhancement of regioselectivity of organic reactions [1], analysis of ion ion interactions [2], and experimental determination of the site of predominant charge localization in anions [3]. The effect of LSR on conformations of difunctional compounds was revealed recently [4]. Although this property of LSR can complicate their use as conformational probes, it may be helpful in modeling interactions between small molecules and biological macromolecules, where biological activity of a small molecule originates from variation of its conformation during association.…”

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Conformational Mobility of Substituted 2-Methoxychalcones under the Action of Lanthanide Shift Reagents

et al. 2005

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Various lanthanide shift reagents Ln(fod) 3 were found to affect the conformational composition of 2-methoxychalcones. Coordination of Yb(fod) 3 occurs mainly at the carbonyl oxygen atom of the substrate, while Eu(fod) 3 and shift reagents derived from other lanthanides coordinate substituted chalcones as bidentate ligands, giving rise to a secondary tetrachelate with the corresponding change of conformation of the substrate molecule. The possibility for chelation is determined by steric hindrances in the vicinity of the substrate coordination centers and concurrent coordination of other electron-donor groups present in the substrate molecule.Lanthanide shift reagents (LSR) have long been used in structural and conformational analysis of organic compounds, studies of their chirality, and interpretation of the NMR spectra. Creation of superconducting spectrometers made it possible to solve many problems without involving LSR. In the recent years, new fields of application of LSR were found, e.g., enhancement of regioselectivity of organic reactions [1], analysis of ion ion interactions [2], and experimental determination of the site of predominant charge localization in anions [3]. The effect of LSR on conformations of difunctional compounds was revealed recently [4]. Although this property of LSR can complicate their use as conformational probes, it may be helpful in modeling interactions between small molecules and biological macromolecules, where biological activity of a small molecule originates from variation of its conformation during association. Therefore, studies on the effect of LSR on molecular conformations in solution seem to be important.Application of LSR is based on their ability to selectively coordinate electron-donor functional groups in the substrates and induce shifts of signals in the NMR spectra; the magnitude of the lanthanide-induced shifts depends on the structure of the LSRsubstrate adduct and arrangement of magnetic nuclei in the substrate molecule relative to the coordination center [5,6]. The structure of LSR adducts with monofunctional organic molecules was extensively studied [7].Complex formation of LSR with difunctional compounds is characterized by some specific features. Most frequently, coordination centers present in a substrate molecule operate independently from each other, and the induced shifts are integral quantities for all possible adducts. If coordination centers in a substrate molecule are spatially close, chelation with LSR is possible to afford tetrakis-adducts in which the coordination number of lanthanide increases to 8 [8]. In order to study this mode of coordination in more detail, we synthesized a series of substituted 1-(2'-alkoxyphenyl)-3-phenyl-2-propenones 5 5 5 5 2 5 5 5 $ , B ;9, D % IXVI, R x = H, unless otherwise stated; I, R 1 = OCH 3 , R 3 = Cl, R 7 = F; II, R 1 = OCH 3 , R 3 = R 5 = Cl; III, R 1 = OCH 3 , R 3 = Br, R 5 = Cl; IV, R 1 = OC 2 H 5 , R 3 = R 7 = Cl; V, R 1 = R 5 = OCH 3 , R 3 = Cl; VI, R 1 = OCH 3 , R 3 = Cl, R 6 R 7 = OCH 2 O; VI...

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Conformational Mobility of Substituted 2-Methoxychalcones under the Action of Lanthanide Shift Reagents

et al. 2005

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Natural and Synthetic Chalcones

Cazarolli¹,

Kappel²,

Zanatta³

et al. 2013

Studies in Natural Products Chemistry

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Eu(fod)3 EFFECT ON 1H NMR SPECTRA OF 3-ARYLISOCOUMARINS AND 3-ARYL-3,4-DIHYDROISOCOUMARINS WITH ALKOXY, ESTER AND AMIDE GROUPS

Khilya

Shablykina

Tsapko

et al. 2017

Bull. T. Shevchenko Nat. Univ. Kyiv. Chem.

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The effect of the lanthanide shift reagent (LSR) – tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octa-dionate) of Europium – Eu(fod)3 – on 1H NMR spectra of functionalized 3-arylisocoumarins and 3-aryl-3,4-dihydroisocoumarins was investigated. Based on previous studies of LSR interactions with benzopyrones, it was expected that the main coordination centre for the Eu3+ would be the exocyclic Oxygen atom of the heterocycle, but the possibility of competition from aromatic substituent functional groups was also considered. By measuring lanthanide-induced shifts (LIS) of the proton signals of the molecules at different ratios of substrate and Eu(fod)3, specific LIS values were determined. Based on those, it was concluded that the main direction of LSR coordination with 3-(2-hydroxy-5-methylphenyl)-1Hisochromen-1-one, 3-(2-methoxy-5-methylphenyl)-1H-isochromen-1-one and 3-(2-methoxy-5-methylphenyl)isochroman-1-one is the exocyclic Oxygen atom of the heterocycle, because the maximum LIS were recorded for the H-8 atom of isochromone system of these derivatives. In the case of ethyl ester of [2-(4-(1-oxo-1H-isochromen-3-yl)phenoxy] acetic acid and methyl ester of [2-(4-(1-oxoisochroman-3-yl)phenoxy]acetic acid comparable LIS values were observed both for H-8 and for the methylene group of the hydroxyacetic acid fragment, therefore, in such molecules the coordination of the Eu3+ to the heterocycle or to the aliphatic ester group is almost equally probable. In spectrum of methyl ester of N-{[4-(1-oxo-1H-isochromen-3-yl)phenoxy]acetyl}valine and N-{[4-(1-oxoisochroman-3-yl)-phenoxy]acetyl}valine there are insignificant LIS of H-8; and the maximum LIS were observed for the signals of the protons neighboring the two carbonyl groups of hydroxyacetic acid and valine fragments. Thus, these compounds interact w

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Conformational Mobility of Substituted 2-Methoxychalcones under the Action of Lanthanide Shift Reagents

Conformational Mobility of Substituted 2-Methoxychalcones under the Action of Lanthanide Shift Reagents

Natural and Synthetic Chalcones

Eu(fod)3 EFFECT ON 1H NMR SPECTRA OF 3-ARYLISOCOUMARINS AND 3-ARYL-3,4-DIHYDROISOCOUMARINS WITH ALKOXY, ESTER AND AMIDE GROUPS

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