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

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

doi:10.1007/s11178-005-0118-x

Cited by 4 publications

(7 citation statements)

References 8 publications

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“…25a–b,27 It is also reported that different coordination modes of Eu(fod) 3 and Yb(fod) 3 may account for their different facial selectivity in HDA reaction. 26 As depicted in Figure 3, the high facial selectivity induced by Yb(fod) 3 is probably ascribed to the different facial steric surrounding. The 7,20-epoxy blocks the α -face, and consequently, the dienophile approaches to the heterodiene mainly from the less hindered β -face in an endo -selective manner.…”

Section: Resultsmentioning

confidence: 96%

ent-Kaurane-based regio- and stereoselective inverse electron demand hetero-Diels–Alder reactions: synthesis of dihydropyran-fused diterpenoids

et al. 2014

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A mild and concise approach for the construction of 3,4-dihydro-2H-pyran ring integrated into the A-ring of the natural product oridonin using an optimized inverse electron demand hetero-Diels-Alder (IED HDA) reaction is reported herein. A self-dimerization of the exocyclic enone installed in the A-ring through a homo-HDA reaction was identified to exclusively give a dimeric ent-kaurane diterpenoid with the spirochroman core. Moreover, the efficient cross-HDA cycloadditions of this enone with various vinyl ethers or vinyl sulfides, instead of its own homo-HDA dimerization, were achieved in regio- and stereoselective manners, thus providing the access to novel dihydropyran-fused diterpenoids as potential anticancer agents to overcome chemoresistance.

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Section: Resultsmentioning

confidence: 96%

ent-Kaurane-based regio- and stereoselective inverse electron demand hetero-Diels–Alder reactions: synthesis of dihydropyran-fused diterpenoids

et al. 2014

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“…Lanthanide (III) complexes, in particular, of the chelate type, are used as tools in the structural analysis with the help of NMR spec-troscopy [1,2]. The LSRs are widely applied when studying the structure of organic compounds, their conformations in solutions, and the enantiomeric purity, as well as to detect the chirality, and so forth [3].…”

Section: Introductionmentioning

confidence: 99%

1H- and 31P-NMR Spectroscopy Study of Paramagnetic Lanthanide Coordination Compounds [LnL3 • Phen] (L = CCl3C(O)NP(O)(OCH3)2)

et al. 2019

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A series of lanthanide coordination compounds with dimethyl-N-trichloroacetylamidophosphate CCl3C(O)N(H)P(O)(OCH3)2 (HL) [HL = CCl3C(O)N(H)P(O)(OCH3)2 is a ligand of the carbacylamidophosphate (CAPh) type], whose compositions are described by the formula [LnL3 · Phen], where Ln = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, and Er; L is the deprotonized form of HL; and Phen is 1,10-Phenantroline, has been synthesized. Acetonic solutions of HL and complexes synthesized on its basis are studied by means of 1H- and 31P-NMR spectroscopy at room temperature (298 K). Since the chemical shifts of 1H signals have the pseudocontactorigin, the isotropic shifts of 31P signals are managed to be decomposed into the contact and pseudocontact components. It is found that there are two series of complexes in the solution of [LnL3 · Phen] compounds with the same structure of the coordination sphere within each of the series Ln = (Ce, Pr, Nd, Sm) (series L1) and Ln = (Tb, Dy, Ho, Er) (series L2). The values of the constant of superfine interaction for those complexes are calculated: 0.18 MHz (series L1) and 0.13 MHz (series L2).

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“…5 The most common practice is to successively add known amounts of LSR to the compound under study and record NMR spectra aer each addition (the shied spectra). 1,[5][6][7][8][9][10][11] In recent years experiments involving chiral LSRs have been successfully carried out for the enantiomeric discrimination of oxygenated bicyclic monoterpenes (bornyl acetate, fenchone and camphor) contained in essential oils, without isolation of the compounds. 3 This approach has been successfully employed in structural and conformational analysis of many synthetic organic compounds and natural products, as well as in the study of their chirality, but it requires the substrate in pure state with known or almost resolved structure on the basis of data from regular NMR measurements.…”

Section: Introductionmentioning

confidence: 99%

“…The application of LSRs is based on their ability to selectively coordinate electron-donor functional groups in the substrates and induce shis of signals in NMR spectra. 5 The most common practice is to successively add known amounts of LSR to the compound under study and record NMR spectra aer each addition (the shied spectra). The chemical shis of some protons and carbons in the substrates alter, to a greater or lesser degree, with each addition of LSR and may result in the segregation of overlapping signals that could facilitate its assignments.…”

Section: Introductionmentioning

confidence: 99%

“…3 This approach has been successfully employed in structural and conformational analysis of many synthetic organic compounds and natural products, as well as in the study of their chirality, but it requires the substrate in pure state with known or almost resolved structure on the basis of data from regular NMR measurements. 1,[5][6][7][8][9][10][11] In recent years experiments involving chiral LSRs have been successfully carried out for the enantiomeric discrimination of oxygenated bicyclic monoterpenes (bornyl acetate, fenchone and camphor) contained in essential oils, without isolation of the compounds. 12,13 Similar methodology was applied in enantiomeric ratio determination of atropine and hyoscyamine in the crude extract of Datura stramonium seeds.…”

Section: Introductionmentioning

confidence: 99%

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Lanthanide-induced shift reagents enable the structural elucidation of natural products in inseparable complex mixtures – the case of elemenal from Inula helenium L. (Asteraceae)

Genčić

Radulović

2015

RSC Adv.

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The use of lanthanide complexes for resolving intricate NMR signals and, in the case of chiral ligands, for determining enantiomeric excess has progressively decreased in the last 30 years. Recently, a sesquiterpene aldehyde from Inula helenium with a possible potent antistaphylococcal activity remained unidentified due to the impossibility of separating the compound from its complex matrix available in very low amounts (ca. 5 mg). Detailed analyses of 1D and 2D NMR spectra of this original complex sample allowed access to a very limited amount of structural data for the unknown aldehyde. We decided to investigate the potential usefulness of lanthanide-induced shift reagents for the resolution and assigning of overlapped 1 H NMR signals originating from different components of this complex mixture (i.e. for a qualitative analysis). The incremental addition of tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III) (Eu(fod) 3 ) led to a simplification of the NMR spectra in terms of signal overlap and removal of chemical shift degeneracy, allowing the mining of crucial data from the shifted NMR spectra. 2D NMR spectra ( 1 H-1 H-COSY, NOESY, HSQC and HMBC) of the sample mixed with Eu(fod) 3 proved to be particularly valuable in this respect. The obtained additional information revealed that the compound in question was a rare sesquiterpeneelemenal (elema-1,3,11(13)-trien-12al). Therefore, herein we report on a new chromatography-free methodology that could be of value in structure elucidation of unknown compounds even if they are not available in a pure state. 18533014; Tel: +381 18533015 † Electronic supplementary information (ESI) available: A comparison of experimental and simulated 1 H NMR spectra of elemenal (the second order vinyl group spin system). Results of the conformational analysis of elemenal-Eu(fod) 3 complex obtained using the lanthanide probe method. See Fig. 6 The chemical shift vs. the ratio of the shift reagent and elemenal plots obtained from the incremental addition of Eu(fod) 3 to elemenal for: (a) the protons closest to the coordination site, (b) the remaining olefinic protons and (c) for the protons that resonated at the high field region.This journal is

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

Cited by 4 publications

References 8 publications

ent-Kaurane-based regio- and stereoselective inverse electron demand hetero-Diels–Alder reactions: synthesis of dihydropyran-fused diterpenoids

ent-Kaurane-based regio- and stereoselective inverse electron demand hetero-Diels–Alder reactions: synthesis of dihydropyran-fused diterpenoids

1H- and 31P-NMR Spectroscopy Study of Paramagnetic Lanthanide Coordination Compounds [LnL3 • Phen] (L = CCl3C(O)NP(O)(OCH3)2)

Lanthanide-induced shift reagents enable the structural elucidation of natural products in inseparable complex mixtures – the case of elemenal from Inula helenium L. (Asteraceae)

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