• Title/Summary/Keyword: Chiral NMR shift agent

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Simple and Efficient Method for the Enantiomeric discrimination of Racemates (라세미 화합물의 거울상 이성질체 구분을 위한 간단하고 효과적인 방법)

  • Ho Sik Rho
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.49 no.2
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    • pp.141-146
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    • 2023
  • The efficient use of a chiral shift agent (3) containing bifunctional group (thiourea and tertiary amine) for the determination of the enantiomeric purity of racemic mixture (Hemiesters) has been studied. The diastereomeric complexes derived from a chiral shift agent (3) with various hemiesters gave rise to well separate signals of the methoxy protons of hemiesters. Good splitting signals for enantiomers of hemiesters in 1H NMR are originated form the hydrogen bonds between carbonyl groups of hemiester and bifunctional groups of a chiral shift agent (3) such as thiourea moiety and tertiary amine. This study provides a quick and simple way to determine the chiral purity of hemiester using chiral transfer agent (3).

$^1$H-NMR Studies of Chiral Solvating Agent Induced - Chemical Shift Differences of Ibuprofen Enantiomers

  • Lee, Jae-Yong;Seo, Sang-Hun;Hong, Seon-Pyo;Kim, Kyeong-Ho
    • Proceedings of the PSK Conference
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    • 2003.10b
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    • pp.223.3-224
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    • 2003
  • Chiral discrimination of ibuprofen by $^1$H-NMR using several chiral solvating agents such as (-)-brucine, (-)-cinchonidine, (1R, 2S)-(-)-ephedrine, (S)-(-)-${\alpha}$- methylbenzylamine, (-)-strychnine and L-(-)-tryptophane was investigated. Racemic ibuprofen treated with one equivalent of chiral solvating agent was preferentially crystallized. Chiral purity of each precipitates was measured by chiral HPLC and chemical shift differences(ΔΔ$\delta$) was calculated. Eventhough (S)-(-)-${\alpha}$-methylbenzylamine was most effective for the preferential recrystalization of (S)-(+)-ibuprofen, chemical shift differentiation ability was weak. (omitted)

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NMR Spectroscopic Analysis on the Chiral Recognition of Noradrenaline by β-Cyclodextrin ( β-CD) and Carboxymethyl- β-cyclodextrin (CM- β-CD)

  • Lee, Sang-Hoo;Yi, Dong-Heui;Jung, Seung-Ho
    • Bulletin of the Korean Chemical Society
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    • v.25 no.2
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    • pp.216-220
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    • 2004
  • ${\beta}$-CD and CM- ${\beta}$-CD as chiral NMR shift agents were used to resolve the enantiomers of noradrenaline (NA). The stoichiometry of each complex formed between the CDs and the enantiomers of NA was found to be 1 : 1 through the continuous variation plots. The binding constants (K) of the complexes were determined from $^1H$ NMR titration curves. This result indicated that both ${\beta}$-CD and CM- ${\beta}$-CD formed the complexes with the S(+)-NA more preferentially than its R(-)-enantiomer. The K values for the complexes with ${\beta}$-CD ($K_{S(+)}$ = 537 $M^{-1}$ and $K_{R(-)}$ = 516 $M^{-1}$ was larger than those with CM- ${\beta}$-CD ($K_{S(+)}$ = 435 $M^{-1}$ and $K_{R(-)}$ = 313 $M^{-1}$), however, enantioselectivity (${\alpha}$) of S(+)- and R(-)-NA to CM- ${\beta}$-CD ( ${\alpha}$ = 1.38) was larger than that to ${\beta}$-CD ( ${\alpha}$ = 1.04), indicating that CM- ${\beta}$-CD was the better chiral NMR solvating agents for the recognition of the enantiomers of NA. Two dimensional rotating frame nuclear Overhauser enhancement spectroscopy (ROESY) experiments were also performed to explain the binding properties in terms of spatial fitting of the NA molecule into the macrocyclic cavities.