Solid‐state ESR differentiation between racemate versus enantiomer

Levkin, Pavel A.; Кокорин, А. И.; Schurig, Volker; Kostyanovsky, Remir G.

doi:10.1002/chir.20242

Cited by 10 publications

(12 citation statements)

References 29 publications

(28 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This conclusion, drawn in ref. , is based not only on the results of calculations, but also on analysis of the reference data . According to EPR data, a two‐fold difference between the HFI constants of optically active stable radicals and biradicals in the solid state and solution had already been observed.…”

Section: Spin Selectivity Of Et In Dyads With (S)‐ and (R)‐npxsupporting

confidence: 83%

“…[21],i sb ased not only on the results of calculations,b ut also on analysis of the reference data. [28][29][30][31][32] According to EPR data, at wo-fold differenceb etween the HFI constantso fo ptically active stable radicals and biradicalsi nt he solid state and solutionh ad already been observed. For the g factors, appreciably smaller changes were observed.…”

Section: Spin Selectivity Of Et In Dyads With (S)-and (R)-npxmentioning

confidence: 99%

See 1 more Smart Citation

Role of Association in Chiral Catalysis: From Asymmetric Synthesis to Spin Selectivity

Ageeva

Khramtsova

Magin

et al. 2018

Chemistry A European J

View full text Add to dashboard Cite

The origin of biomolecules in the pre-biological period is still a matter of debate, as is the unclarified nature of the differences in enantiomer properties, especially for the medically important activity of chiral drugs. With regards to the first issue, significant progress was made in the last decade of the 20th century through experimental confirmation of Frank's popular theory on chiral catalysis in spontaneous asymmetric synthesis. Soai examined the chiral catalysis of the alkylation of achiral aldehydes by achiral reagents. Attempts to model this process demonstrated the key role of chiral compounds associates as templates for chiral synthesis. However, the elementary mechanism of alkylation and the role of free radicals in this process are still incompletely understood. Meanwhile, the influence of external magnetic fields on chiral enrichment in the radical path of alkylation has been predicted. In addition, the role of chiral dyad association in another radical process, electron transfer (ET), has been recently demonstrated by the following methods: chemically induced dynamic nuclear polarisation (CIDNP), NMR spectroscopy, XRD and photochemistry. The CIDNP analysis of ET in two dyads has revealed a phenomenon first observed for chiral systems, spin selectivity, which results in the difference between the CIDNP enhancement coefficients of dyad diastereomers. These dyads are linked systems consisting of the widespread drug (S)-naproxen (NPX) or its R analogue and electron donors, namely, (S)-tryptophan and (S)-N-methylpyrrolidine. Because NPX is one of the most striking examples of the difference in the therapeutic properties of enantiomers, the appearance of spin selectivity in dyads with (S)- and (R)-NPX and S donors can shed light on the chemical nature of these differences. This review is devoted to discussing the chemical nature of spin selectivity and the role of chiral associates in the chiral catalysis of an elementary radical reaction: ET in chiral dyads.

show abstract

Section: Spin Selectivity Of Et In Dyads With (S)‐ and (R)‐npxsupporting

confidence: 83%

Section: Spin Selectivity Of Et In Dyads With (S)-and (R)-npxmentioning

confidence: 99%

Role of Association in Chiral Catalysis: From Asymmetric Synthesis to Spin Selectivity

Ageeva

Khramtsova

Magin

et al. 2018

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…On the other hand, EPR studies of the paramagnetic forms of individual opticali somers and racemates in solids [8,10] and solutions [11][12][13][14] have shown differences between the values of hyperfine interaction constants (HFIs), g factors, and electron exchange interaction energy (J). In thesew orks, individual chiral isomers and racemates of stable nitroxyl radicals and biradicals werestudied.…”

Section: Introductionmentioning

confidence: 99%

“…In thesew orks, individual chiral isomers and racemates of stable nitroxyl radicals and biradicals werestudied. [8,[10][11][12][13][14] Herein, we consider the various causes of spin selectivity 1 in the photoinduced ET of (R,S)-and (S,S)-diastereomers of two NPX-based dyads ( Figure 1). The differences in the experimental CIDNP enhancement coefficients were compared with those calculated in the framework of the model in which HFI constants, g-factor differences, and lifetimes of paramagnetic forms of diastereomers were varied.…”

Section: Introductionmentioning

confidence: 99%

Spin Selectivity in Chiral Linked Systems

Ageeva

Khramtsova

Magin

et al. 2018

Chemistry A European J

105

View full text Add to dashboard Cite

This work has shown spin selectivity in electron transfer (ET) of diastereomers of (R,S)-naproxen-(S)-N-methylpyrrolidine and (R,S)-naproxen-(S)-tryptophan dyads. Photoinduced ET in these dyads is interesting because of the still unexplained phenomenon of stereoselectivity in the drug activity of enantiomers. The chemically induced dynamic nuclear polarization (CIDNP) enhancement coefficients of (R,S)-diastereomers are double those of the (S,S)-analogue. These facts are also interesting because spin effects are among the most sensitive, even to small changes in spin and molecular dynamics of paramagnetic particles. Therefore, CIDNP reflects the difference in magnetoresonance parameters (hyperfine interaction constants (HFIs), g-factor difference) and lifetimes of the paramagnetic forms of (R,S)- and (S,S)-diastereomers. The difference in HFI values for diastereomers has been confirmed by a comparison of CIDNP experimental enhancement coefficients with those calculated. Additionally, the dependence of the CIDNP enhancement coefficients on diastereomer concentration has been observed for the naproxen-N-methylpyrrolidine dyad. This has been explained by the participation of ET in homo-(R,S-R,S or S,S-S,S) and hetero-(R,S-S,S) dimers of dyads. In this case, the effectivity of ET, and consequently, CIDNP, is supposed to be different for (R,S)- and (S,S)-homodimers, heterodimers, and monomers. The possibility of dyad dimer formation has been demonstrated by using high-resolution X-ray and NMR spectroscopy techniques.

show abstract

“…Recently, a number of binary chiral stationary phases (CSPs) for enantioselective gas chromatography with an extended spectrum of enantioselectivity were synthesized [47][48][49][50][51] from -valine-diamide and alkylated cyclodextrin selectors. These results prompted us to probe the potential of hep-…”

Section: Introductionmentioning

confidence: 99%

Heptakis[2,3‐di‐O‐methyl‐6‐O‐(L‐valine‐tert‐butylamide‐N^α‐ylcarbonylmethyl)]‐β‐cyclodextrin: a New Multifunctional Cyclodextrin CSA for the NMR Enantiodiscrimination of Polar and Apolar Substrates

et al. 2007

Self Cite

View full text Add to dashboard Cite

Heptakis[2,3‐di‐O‐methyl‐6‐O‐(L‐valine‐tert‐butylamide‐Nα‐ylcarbonylmethyl)]‐β‐cyclodextrin with methyl groups on the secondary sites and a diamide chiral selector on the primary ones showed considerable utility as a CSA in the NMR enantiodiscrimination of a wide spectrum of amino acid derivatives, while also allowing trisubstituted allenes to be enantiodiscriminated. Enantiodiscrimination processes were investigated by Diffusion‐Ordered SpectroscopY (DOSY). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

show abstract

Solid‐state ESR differentiation between racemate versus enantiomer

Abstract: Noticeable differences between solid-state ESR spectra of enantiopure and racemic single crystals as well as powders of 2,2,5,5-tetramethylpyrrolidine-3-carboxamide-1-oxyl have been observed. Possible reasons of this fact are proposed.

Cited by 10 publications

References 29 publications

Role of Association in Chiral Catalysis: From Asymmetric Synthesis to Spin Selectivity

Role of Association in Chiral Catalysis: From Asymmetric Synthesis to Spin Selectivity

Spin Selectivity in Chiral Linked Systems

Heptakis[2,3‐di‐O‐methyl‐6‐O‐(L‐valine‐tert‐butylamide‐N^α‐ylcarbonylmethyl)]‐β‐cyclodextrin: a New Multifunctional Cyclodextrin CSA for the NMR Enantiodiscrimination of Polar and Apolar Substrates

Contact Info

Product

Resources

About

Solid‐state ESR differentiation between racemate versus enantiomer

Abstract: Noticeable differences between solid-state ESR spectra of enantiopure and racemic single crystals as well as powders of 2,2,5,5-tetramethylpyrrolidine-3-carboxamide-1-oxyl have been observed. Possible reasons of this fact are proposed.

Cited by 10 publications

References 29 publications

Role of Association in Chiral Catalysis: From Asymmetric Synthesis to Spin Selectivity

Role of Association in Chiral Catalysis: From Asymmetric Synthesis to Spin Selectivity

Spin Selectivity in Chiral Linked Systems

Heptakis[2,3‐di‐O‐methyl‐6‐O‐(L‐valine‐tert‐butylamide‐Nα‐ylcarbonylmethyl)]‐β‐cyclodextrin: a New Multifunctional Cyclodextrin CSA for the NMR Enantiodiscrimination of Polar and Apolar Substrates

Contact Info

Product

Resources

About

Heptakis[2,3‐di‐O‐methyl‐6‐O‐(L‐valine‐tert‐butylamide‐N^α‐ylcarbonylmethyl)]‐β‐cyclodextrin: a New Multifunctional Cyclodextrin CSA for the NMR Enantiodiscrimination of Polar and Apolar Substrates