Reversed phase chromatographic resolution of amino acid enantiomers with metal-Aspartam eluants

Gilon, Chaim; Leshem, R.; Tapuhi, Yitzhak; Grushka, Eli

doi:10.1021/ja00519a024

Cited by 69 publications

(12 citation statements)

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“…A Cu(II)-aspartame complex has been used for resolution of amino acid enantiomers by capillary electrophoresis (Gozel et al, 1986) and HPLC (Gilon et al, 1979). Cu(II) readily forms 1:1 and 1:2 complexes with aspartame, with the 1:1 complex predominating below pH 4 (Aihara et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

“…It is likely that the Cu(II) present in the reaction mixtures is coordinated to aspartame, which may alter the rates and specificities of these reactions relative to the aquated Cu(II) ion. A Cu(II)-aspartame complex has been used for resolution of amino acid enantiomers by capillary electrophoresis (Gozel et al, 1986) and HPLC (Gilon et al, 1979). Cu(II) readily forms 1:1 and 1:2 complexes with aspartame, with the 1:1 complex predominating below pH 4 (Aihara et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

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Benzaldehyde Formation from Aspartame in the Presence of Ascorbic Acid and Transition Metal Catalyst

Lawrence

Dong-mei

1996

J. Agric. Food Chem.

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Benzaldehyde was produced from aspartame in aqueous acidic solutions containing ascorbic acid and Cu(II) or Fe(III) ion. Benzaldehyde was identified in the system by GC−MS. The yield of benzaldehyde decreases dramatically as the pH of the medium increases above 2.0. EDTA and DTPA completely inhibited benzaldehyde production, while desferrioxamine inhibited only the Fe(III)-catalyzed reaction. Benzaldehyde is not produced under anaerobic conditions unless H2O2 is added to reaction mixtures. H2O2 is produced by reduction of atmospheric oxygen under aerobic conditions. Benzaldehyde production was dependent on ascorbic acid concentration, but the yield of benzaldehyde decreased as the concentration of ascorbic acid exceeded that of aspartame. Addition of ethanol to the reaction mixture had little or no effect on benzaldehyde production, suggesting a mechanism that may not involve free hydroxyl radical. A mechanism is proposed for the reaction. Keywords: Aspartame; benzaldehyde; ascorbic acid; free radical degradation products; copper(II)

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Benzaldehyde Formation from Aspartame in the Presence of Ascorbic Acid and Transition Metal Catalyst

Lawrence

Dong-mei

1996

J. Agric. Food Chem.

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“…The greater the hydrophobicity of the α-amino acid side chain, the greater is the interaction between the L-α-amino acid and the L-ligand, and the greater is the retentivity of the pseudo-homochiral complex. 8,10,12,31 Having in mind the structural relationship between Lhydroxyproline and DL-threonine and DL-serine, it would be expected that there would be a more reliable chiral recognition between the L-ligand and these hydroxy amino acids than with the compounds lacking the hydroxy group. However, no enantioseparation was achieved in these cases (DL-threonine and DL-serine) or with less hydrophobic α-amino acids ( Table 2), indicating that the presence of a polar hydroxy group in the chiral selector decreased the hydrophobic interaction of the diastereoisomeric complexes and the stationary phase.…”

Section: The Hydrophobic Interaction Between Chiral Selectors and α-Amentioning

confidence: 99%

Chiral Ligand Exchange Chromatography: Separation of Enantiomeric Mixtures of Underivatized α-Amino Acids under UV Detection

Nazareth¹,

Antunes²

2002

J. Braz. Chem. Soc.

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) em água ou em água/ metanol. A utilização de água/metanol leva a uma grande diminuição dos tempos de retenção dos α-amino ácidos mais hidrofóbicos, preservando a separação enantiomérica. O pH precisa ser alto o bastante para permitir a presença de grupos -NH 2 livres, o que torna a complexação com Cu(II) mais fácil. α-Amino ácidos conformacionalmente mais restritos, como a L-prolina e a L-hidroxiprolina, conduziram a separações enantioméricas menores. A formação de complexos pseudo-homoquirais e pseudo-heteroquirais, por troca de ligantes, que é cinética e termodinamicamente controlada, desempenha um papel fundamental para a separação enantiomérica desejada. Esta metodologia simples e barata pode ser usada em qualquer laboratório envolvido em síntese de α-amino ácidos.Enantiomeric mixtures of alanine, serine, threonine, valine, methionine, leucine and norleucine were resolved in ligand exchange reversed phase HPLC (reproducibly), by using L-proline, L-) and Cu(CH 3 COO) 2 (1 mmol L -1 ) in water or in water/methanol. The latter mobile phase greatly decreased the retention time of the more hydrophobic α-amino acids, preserving enantioseparation. pH must be high enough to allow the presence of free -NH 2 groups in order to make the complexation with Cu(II) easier. The more restricted conformation of L-proline and L-hydroxyproline led to lower enantioseparations. The ligand exchange formation of pseudo-homochiral and pseudo-heterochiral complexes, thermodynamically and kinetically controlled, plays a fundamental role for the desired enantiomeric chromatographic separation. This simple and inexpensive methodology can be used routinely by any laboratory involved in α-amino acid synthesis.

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“…One approach has been to covalently bond a chiral ligand to the solid support of the chromatographic column (2)(3)(4)(5). Another has been to add a chiral ligand and metal ion to the eluant phase (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). This latter method is particularly attractive because the eluant is easily prepared by mixing solutions containing the metal ion and ligand and adjusting the pH to an appropriate value.…”

mentioning

confidence: 99%

“…An intriguing reagent, which may operate through both mechanisms, is the Cu(II) complex of L-aspartyl-L-phenylalanine methyl ester (aspartame) (7). Originally this reagent was thought to operate via mobile phase interactions (7), but later experiments using analogous L-aspartyl-c-hexylamine derivatives led to the conclusion that stationary phase reactions were important (15). We report here the results of an in-depth study of the separation of D-and L-valine using mobile phase solutions of Cu(II) and aspartame.…”

mentioning

confidence: 99%

Mechanism of the reversed-phase high-performance liquid chromatographic separation of D- and L-valine using copper(II) and L-aspartyl-L-phenylalanine methyl ester

Broge¹,

Leussing²

1986

Anal. Chem.

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Reversed phase chromatographic resolution of amino acid enantiomers with metal-Aspartam eluants

Cited by 69 publications

References 0 publications

Benzaldehyde Formation from Aspartame in the Presence of Ascorbic Acid and Transition Metal Catalyst

Benzaldehyde Formation from Aspartame in the Presence of Ascorbic Acid and Transition Metal Catalyst

Chiral Ligand Exchange Chromatography: Separation of Enantiomeric Mixtures of Underivatized α-Amino Acids under UV Detection

Mechanism of the reversed-phase high-performance liquid chromatographic separation of D- and L-valine using copper(II) and L-aspartyl-L-phenylalanine methyl ester

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