Chiral NMR discrimination of amines: Analysis of secondary, tertiary, and prochiral amines using (18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

Lovely, Ann E.; Wenzel, Thomas J.

doi:10.1002/chir.20449

Cited by 38 publications

(12 citation statements)

References 25 publications

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“…The crown ether (18-crown-6)-2,3,11,12-tetracarboxylic acid has been used in water as a chiral solvating agent for primary amines, 30 although the enantiomeric discrimination with this crown ether is better in methanol and acetonitrile. [30][31][32][33][34][35][36][37][38] Calixarenes and calix [4]resorcinarenes are two other important families of cavity compounds, [39][40][41][42] although these have found limited application in NMR spectro-scopy. 1,[43][44][45][46][47][48][49][50][51] One exception is a tetrasulfonated calix [4] resorcinarene that contains optically pure L-prolinylmethyl groups (1).…”

Section: Introductionmentioning

confidence: 99%

Water‐soluble calix[4]resorcinarenes as chiral NMR solvating agents for bicyclic aromatic compounds

2009

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Water-soluble calix[4]resorcinarenes with proline, 3-hydroxyproline, and 4-hydroxyproline substituent groups are evaluated as chiral NMR solvating agents on a series of bicyclic aromatic compounds with naphthyl, indole, dihydroindole, and indane rings. The substrates interact with the calixresorcinarene through insertion of the aromatic ring into the cavity. Most of the substrates are analyzed as cationic species, although one anionic species is analyzed. All of the substrates exhibit enantiomeric discrimination in the 1H-NMR spectrum with one or more of the calixresorcinarenes. In most cases, the hydroxyproline derivatives are more effective at causing enantiodifferentiation than the corresponding proline derivative. Presumably, the hydroxyl group on the proline moieties is involved in interactions with the substituent groups of the substrate that are important in creating chiral recognition. The enantiomeric discrimination in the 1H-NMR spectrum is large enough for many resonances to permit the analysis of enantiomeric purity.

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Section: Introductionmentioning

confidence: 99%

Water‐soluble calix[4]resorcinarenes as chiral NMR solvating agents for bicyclic aromatic compounds

2009

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“…Previously, secondary amino compounds were proposed to be resolved on CSP 1 through the ionic interaction between the cationic site of the protonated secondary amines and anionic carboxylate group of the CSP and the two N–H + ···O hydrogen bonds between the secondary ammonium ions (RR′‐NH 2 + ) and the crown ether ring of the CSP as shown in Figure A . The ionic interaction shown in Figure A has also been proposed from NMR spectroscopy of the recognition of secondary amines using (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid as a NMR chiral solvating agent . The identical chiral recognition mechanism might be applied to the resolution of methoxyphenamine ( 3 ) on CSP 2 as shown in Figure B.…”

Section: Resultsmentioning

confidence: 92%

Resolution of methoxyphenamine and its analogues on a chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

Jeon

Hyun

2018

J of Separation Science

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A liquid chromatographic chiral stationary phase, which contains two N–CH3 amide connecting groups, based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid was first applied to the resolution of methoxyphenamine (2‐methoxy‐N‐methylamphetamine, a β‐adrenergic receptor agonist used as a bronchodilator). The resolution of methoxyphenamine on the chiral stationary phase containing two N–CH3 amide connecting groups was quite successful with the separation factor (α) of 1.42 and resolution (RS) of 4.22 compared with those (α of 1.09 and RS of 1.55) on the chiral stationary phase containing two N–H amide connecting groups. In addition, the chiral stationary phase containing two N–CH3 amide connecting groups was applied to the resolution of methoxyphenamine analogues. From the comparison of the resolution results of methoxyphenamine with those of methoxyphenamine analogues on the chiral stationary phase containing two N–CH3 amide connecting groups, the N‐methyl group and the 2‐methoxyphenyl group of methoxyphenamine were elucidated to be the structurally essential parts for the resolution on the chiral stationary phase.

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“…Previous studies with x-ray crystallography and nuclear magnetic resonance spectroscopy have demonstrated the affinity of 18c6H 4 for protonated amines, amino acids, amino alcohols and further compounds with free amino functionality. [8][9][10][11][12][13][14][15][16] Those studies have provided evidence for the relevance of the barrel-like and bowl-like structures adopted by 18c6H 4 . Such structures are sustained by intramolecular H-bonding involving the carboxyl groups and by intermolecular interactions of the cationic guest with the ether and carboxyl oxygen atoms.…”

Section: Introductionmentioning

confidence: 86%

Multipodal coordination of a tetracarboxylic crown ether with ${\rm NH}_4^+$ NH 4+: A vibrational spectroscopy and computational study

Hurtado

Gámez

Hamad

et al. 2012

The Journal of Chemical Physics

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The elucidation of the structural requirements for molecular recognition by the crown ether (18-crown-6)-2,3,11,12-tetracarboxylic acid (18c6H(4)) and its cationic complexes constitutes a topic of current fundamental and practical interest in catalysis and analytical sciences. The flexibility of the central ether ring and its four carboxyl side arms poses important challenges to experimental and theoretical approaches. In this study, infrared action vibrational spectroscopy and quantum mechanical computations are employed to characterize the conformational structure of the isolated gas phase complex formed by the 18c6H(4) host with NH(4)(+) as guest. The results show that the most stable gas-phase structure is a barrel-like conformation sustained by tetrapodal H-bonding of the ammonia cation with two C=O side groups and with four oxygen atoms of the ether ring in a bifurcated arrangement. Interestingly, a similar structure had been proposed in previous crystallographic studies. The experiment also provides evidence for a significant contribution of a higher energy bowl-like conformer with features resembling those adopted by 18c6H(4) in the analogous complexes with secondary amines. Such a conformation displays H-bonding between confronted side carboxyl groups and tetrapodal binding of the NH(4)(+) with the ether ring and with one C=O group. Structures involving even more extensive intramolecular H-bonding in the 18c6H(4) substrate are found to lie higher in energy and are ruled out by the experiment.

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Chiral NMR discrimination of amines: Analysis of secondary, tertiary, and prochiral amines using (18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

Cited by 38 publications

References 25 publications

Water‐soluble calix[4]resorcinarenes as chiral NMR solvating agents for bicyclic aromatic compounds

Water‐soluble calix[4]resorcinarenes as chiral NMR solvating agents for bicyclic aromatic compounds

Resolution of methoxyphenamine and its analogues on a chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

Multipodal coordination of a tetracarboxylic crown ether with ${\rm NH}_4^+$ NH 4+: A vibrational spectroscopy and computational study

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