Chiral recognition of (18-crown-6)-tetracarboxylic acid as a chiral selector determined by NMR spectroscopy

Eunjung Bang, Dai Woon Lee, Wonjae Lee, Jin Won Jung, Weon Tae Lee

Research output: Contribution to journalArticle

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Abstract

It is shown that the chiral selector (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) employed for resolution of α-amino acids in capillary electrophoresis and in chiral HPLC can be used for resolution of α-amino acids and ester derivatives in NMR experiments. In a quest for the origin of chiral recognition of α-amino acids in the presence of 18-C-6-TA as a chiral selector, these interactions responsible for the differential affinities shown toward enantiomers are investigated by NMR spectroscopy. Chemical-shift differences of the corresponding 1H and 13C resonances of D-and L-phenylglycine (PG) or phenylglycine methyl ester (PG-ME) show that most chemical shifts in the presence of 18-C-6-TA moved in the same direction (i.e., upfield or downfield) as compared with those of the free state. Significant reduction of the T1-values is observed for the host-guest complex molecules, indicating that the mobility of the isomers is significantly reduced due to tight binding with 18-C-6-TA. NMR line broadening of the analyte upon complexation further supports this finding. The observed intermolecular NOEs of the α-proton and ortho phenyl protons of PG or PG-ME in the presence of 18-C-6-TA are used for generating structures for 18-C-6-TA/enantiomer complexes. Molecular dynamics calculations based on NOEs illustrate the essential features of the chiral recognition mechanism: 1) three +NH ··· O hydrogen bonds in a tripod arrangement between polyether oxygens of 18-C-6-TA and the ammonium moiety of the enantiomer; 2) a hydrophobic interaction between the polyether ring of 18-C-6-TA and the phenyl moiety of the enantiomer; 3) hydrogen bonding between the carboxylic acid of 18-C-6-TA and the carbonyl oxygen of the D-enantiomer.

Original languageEnglish
Pages (from-to)1685-1692
Number of pages8
JournalJournal of the Chemical Society, Perkin Transactions 2
Volume9
DOIs
Publication statusPublished - 2001 Jan 1

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Enantiomers
Nuclear magnetic resonance spectroscopy
Polyethers
Chemical shift
Amino Acids
Protons
Hydrogen bonds
Nuclear magnetic resonance
Oxygen
Capillary electrophoresis
Carboxylic Acids
Complexation
Ammonium Compounds
Isomers
Molecular dynamics
Esters
18-crown-6 2,3,11,12-tetracarboxylic acid
Derivatives
Molecules
2-phenylglycine

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

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title = "Chiral recognition of (18-crown-6)-tetracarboxylic acid as a chiral selector determined by NMR spectroscopy",
abstract = "It is shown that the chiral selector (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) employed for resolution of α-amino acids in capillary electrophoresis and in chiral HPLC can be used for resolution of α-amino acids and ester derivatives in NMR experiments. In a quest for the origin of chiral recognition of α-amino acids in the presence of 18-C-6-TA as a chiral selector, these interactions responsible for the differential affinities shown toward enantiomers are investigated by NMR spectroscopy. Chemical-shift differences of the corresponding 1H and 13C resonances of D-and L-phenylglycine (PG) or phenylglycine methyl ester (PG-ME) show that most chemical shifts in the presence of 18-C-6-TA moved in the same direction (i.e., upfield or downfield) as compared with those of the free state. Significant reduction of the T1-values is observed for the host-guest complex molecules, indicating that the mobility of the isomers is significantly reduced due to tight binding with 18-C-6-TA. NMR line broadening of the analyte upon complexation further supports this finding. The observed intermolecular NOEs of the α-proton and ortho phenyl protons of PG or PG-ME in the presence of 18-C-6-TA are used for generating structures for 18-C-6-TA/enantiomer complexes. Molecular dynamics calculations based on NOEs illustrate the essential features of the chiral recognition mechanism: 1) three +NH ··· O hydrogen bonds in a tripod arrangement between polyether oxygens of 18-C-6-TA and the ammonium moiety of the enantiomer; 2) a hydrophobic interaction between the polyether ring of 18-C-6-TA and the phenyl moiety of the enantiomer; 3) hydrogen bonding between the carboxylic acid of 18-C-6-TA and the carbonyl oxygen of the D-enantiomer.",
author = "Eunjung Bang and Lee, {Dai Woon} and Wonjae Lee and Jung, {Jin Won} and Lee, {Weon Tae}",
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Chiral recognition of (18-crown-6)-tetracarboxylic acid as a chiral selector determined by NMR spectroscopy. / Bang, Eunjung; Lee, Dai Woon; Lee, Wonjae; Jung, Jin Won; Lee, Weon Tae.

In: Journal of the Chemical Society, Perkin Transactions 2, Vol. 9, 01.01.2001, p. 1685-1692.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Chiral recognition of (18-crown-6)-tetracarboxylic acid as a chiral selector determined by NMR spectroscopy

AU - Bang, Eunjung

AU - Lee, Dai Woon

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AU - Lee, Weon Tae

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N2 - It is shown that the chiral selector (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) employed for resolution of α-amino acids in capillary electrophoresis and in chiral HPLC can be used for resolution of α-amino acids and ester derivatives in NMR experiments. In a quest for the origin of chiral recognition of α-amino acids in the presence of 18-C-6-TA as a chiral selector, these interactions responsible for the differential affinities shown toward enantiomers are investigated by NMR spectroscopy. Chemical-shift differences of the corresponding 1H and 13C resonances of D-and L-phenylglycine (PG) or phenylglycine methyl ester (PG-ME) show that most chemical shifts in the presence of 18-C-6-TA moved in the same direction (i.e., upfield or downfield) as compared with those of the free state. Significant reduction of the T1-values is observed for the host-guest complex molecules, indicating that the mobility of the isomers is significantly reduced due to tight binding with 18-C-6-TA. NMR line broadening of the analyte upon complexation further supports this finding. The observed intermolecular NOEs of the α-proton and ortho phenyl protons of PG or PG-ME in the presence of 18-C-6-TA are used for generating structures for 18-C-6-TA/enantiomer complexes. Molecular dynamics calculations based on NOEs illustrate the essential features of the chiral recognition mechanism: 1) three +NH ··· O hydrogen bonds in a tripod arrangement between polyether oxygens of 18-C-6-TA and the ammonium moiety of the enantiomer; 2) a hydrophobic interaction between the polyether ring of 18-C-6-TA and the phenyl moiety of the enantiomer; 3) hydrogen bonding between the carboxylic acid of 18-C-6-TA and the carbonyl oxygen of the D-enantiomer.

AB - It is shown that the chiral selector (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) employed for resolution of α-amino acids in capillary electrophoresis and in chiral HPLC can be used for resolution of α-amino acids and ester derivatives in NMR experiments. In a quest for the origin of chiral recognition of α-amino acids in the presence of 18-C-6-TA as a chiral selector, these interactions responsible for the differential affinities shown toward enantiomers are investigated by NMR spectroscopy. Chemical-shift differences of the corresponding 1H and 13C resonances of D-and L-phenylglycine (PG) or phenylglycine methyl ester (PG-ME) show that most chemical shifts in the presence of 18-C-6-TA moved in the same direction (i.e., upfield or downfield) as compared with those of the free state. Significant reduction of the T1-values is observed for the host-guest complex molecules, indicating that the mobility of the isomers is significantly reduced due to tight binding with 18-C-6-TA. NMR line broadening of the analyte upon complexation further supports this finding. The observed intermolecular NOEs of the α-proton and ortho phenyl protons of PG or PG-ME in the presence of 18-C-6-TA are used for generating structures for 18-C-6-TA/enantiomer complexes. Molecular dynamics calculations based on NOEs illustrate the essential features of the chiral recognition mechanism: 1) three +NH ··· O hydrogen bonds in a tripod arrangement between polyether oxygens of 18-C-6-TA and the ammonium moiety of the enantiomer; 2) a hydrophobic interaction between the polyether ring of 18-C-6-TA and the phenyl moiety of the enantiomer; 3) hydrogen bonding between the carboxylic acid of 18-C-6-TA and the carbonyl oxygen of the D-enantiomer.

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