Synthesis and circular dichroism studies of N,N-bis(2-quinolylmethyl)amino acid Cu(II) complexes: Determination of absolute configuration and enantiomeric excess by the exciton coupling method

Andrea E. Holmes, Steffen Zahn, James Canary

Research output: Contribution to journalArticle

Abstract

We report a method to determine the absolute configuration of α-amino acids by exciton coupled circular dichroism (ECCD). Naturally occurring amino acids were successfully derivatized with 2-bromomethylquinoline. Complexation of these conformationally flexible ligands with Cu(II) salts yielded defined propeller-like structures. The direction of the twist (i.e., the relative orientation of the chromophores to each other) is governed by the asymmetric amino acid carbon center. The transition moments of the chromophores couple and yield a bisignate circular dichroism spectrum, the sign of which corresponds to the absolute configuration of the chiral center of the amino acid. Enantiomeric excess (e.e.) of amino acid derivatives is linearly related to the differential extinction coefficient Δψ and can be assessed easily utilizing a standard curve. This efficient, sensitive technique requires low analyte concentrations, offers several advantages over established methods, and could be applied in medicinal, pharmaceutical, or chemical retail and manufacturing industry.

Original languageEnglish (US)
Pages (from-to)471-477
Number of pages7
JournalChirality
Volume14
Issue number6
DOIs
StatePublished - 2002

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Dichroism
Circular Dichroism
Excitons
Amino acids
Amino Acids
Chromophores
Chemical Industry
Propellers
Complexation
Drug products
Carbon
Salts
Ligands
LDS 751
Derivatives
Pharmaceutical Preparations
Industry

Keywords

  • Absolute configuration
  • Amino acids
  • Chirality
  • Enantiomeric excess
  • Exciton coupled circular dichroism

ASJC Scopus subject areas

  • Analytical Chemistry
  • Organic Chemistry
  • Drug Discovery
  • Pharmacology

Cite this

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title = "Synthesis and circular dichroism studies of N,N-bis(2-quinolylmethyl)amino acid Cu(II) complexes: Determination of absolute configuration and enantiomeric excess by the exciton coupling method",
abstract = "We report a method to determine the absolute configuration of α-amino acids by exciton coupled circular dichroism (ECCD). Naturally occurring amino acids were successfully derivatized with 2-bromomethylquinoline. Complexation of these conformationally flexible ligands with Cu(II) salts yielded defined propeller-like structures. The direction of the twist (i.e., the relative orientation of the chromophores to each other) is governed by the asymmetric amino acid carbon center. The transition moments of the chromophores couple and yield a bisignate circular dichroism spectrum, the sign of which corresponds to the absolute configuration of the chiral center of the amino acid. Enantiomeric excess (e.e.) of amino acid derivatives is linearly related to the differential extinction coefficient Δψ and can be assessed easily utilizing a standard curve. This efficient, sensitive technique requires low analyte concentrations, offers several advantages over established methods, and could be applied in medicinal, pharmaceutical, or chemical retail and manufacturing industry.",
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T1 - Synthesis and circular dichroism studies of N,N-bis(2-quinolylmethyl)amino acid Cu(II) complexes

T2 - Determination of absolute configuration and enantiomeric excess by the exciton coupling method

AU - Holmes, Andrea E.

AU - Zahn, Steffen

AU - Canary, James

PY - 2002

Y1 - 2002

N2 - We report a method to determine the absolute configuration of α-amino acids by exciton coupled circular dichroism (ECCD). Naturally occurring amino acids were successfully derivatized with 2-bromomethylquinoline. Complexation of these conformationally flexible ligands with Cu(II) salts yielded defined propeller-like structures. The direction of the twist (i.e., the relative orientation of the chromophores to each other) is governed by the asymmetric amino acid carbon center. The transition moments of the chromophores couple and yield a bisignate circular dichroism spectrum, the sign of which corresponds to the absolute configuration of the chiral center of the amino acid. Enantiomeric excess (e.e.) of amino acid derivatives is linearly related to the differential extinction coefficient Δψ and can be assessed easily utilizing a standard curve. This efficient, sensitive technique requires low analyte concentrations, offers several advantages over established methods, and could be applied in medicinal, pharmaceutical, or chemical retail and manufacturing industry.

AB - We report a method to determine the absolute configuration of α-amino acids by exciton coupled circular dichroism (ECCD). Naturally occurring amino acids were successfully derivatized with 2-bromomethylquinoline. Complexation of these conformationally flexible ligands with Cu(II) salts yielded defined propeller-like structures. The direction of the twist (i.e., the relative orientation of the chromophores to each other) is governed by the asymmetric amino acid carbon center. The transition moments of the chromophores couple and yield a bisignate circular dichroism spectrum, the sign of which corresponds to the absolute configuration of the chiral center of the amino acid. Enantiomeric excess (e.e.) of amino acid derivatives is linearly related to the differential extinction coefficient Δψ and can be assessed easily utilizing a standard curve. This efficient, sensitive technique requires low analyte concentrations, offers several advantages over established methods, and could be applied in medicinal, pharmaceutical, or chemical retail and manufacturing industry.

KW - Absolute configuration

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KW - Chirality

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