• Biotechnology and Bioprocess Engineering:BBE
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• 제5권1호
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• pp.17-22
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• 2000

The separation of tryptophan enantiomers was carried out with medium-pressure liquid chromatography using BSA (bovine serum albumin)-bonded silica as a chiral stationary phase. The influence of various experimental factors such as pH and ionic strength of mobile phase, separation temperature, and the presence of organic additives on the resolution was studied. In order to expand this system to preparative scale, the loadability of sample and the stability of stationary phase for repeated use were also examined. The separation of tryptophan enantiomers was successful with this system. The data indicated that a higher separation factor (a) was obtained at a higher pH and lower temperature and ionic strength in mobile phase. Addition of organic additives (acetonitrile and 2-propanol) in mobile phase contributed to reduce the retention time of L-tryptophan. About $30\%$ of the separation factor was reduced after 80 days of repeated use.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.415-418
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• 2009

Concerned with ambiguous stereochemistry assignment of natural (+)-glabridin, absolute configurations of (${\pm}$)-glabridin enantiomers were studied with synthetic glabridin. Synthetic glabridin enantiomers were separated by semi-preparative Sumi-chiral column chromatography, and characterized by UV-Vis and NMR spectroscopy. Three-dimensional molecular structure of glabridin was obtained as equatorial Ph-3 half chair chroman ring from semi-empirical PM3 calculation, and refined by coupling constants in $^1H$ NMR spectrum. Finally, absolute configurations of two enantiomers were determined by circular dichroism spectroscopy based on the empirical helicity rules. Absolute configuration of natural (+)-glabridin was confirmed as (R)-glabridin, as known.

• Preventive Nutrition and Food Science
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• 제13권2호
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• pp.134-137
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• 2008

This study was conducted to investigate the effect of pH on the formation of acrylamide and acrylate from glucose and fructose reacting with amino acid enantiomers by the Maillard reaction. The acrylamide content was increased with increasing pH, except for Fru/D-Asn system. Both acrylamide and acrylate contents were higher in the glucose-based system compared to the fructose-based system at pH 10.0. However, according to amino acid enantiomers, only the acrylamide content showed a difference in the fructose-based system. In addition, the acrylate content was increased with increasing pH except in the Glc/L-Asn system. Acrylate formation was observed specifically at pH 4.0 for both the Glc/D-Asn and Fru/D-Asn systems.

• 대한화학회지
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• 제36권6호
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• pp.849-856
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• 1992

간단하고, 경제적이고, 다양한 응용이 가능한 시스템을 이용하여 거울상 이성질체를 분리 및 분취하였다. 소수성 아미노산 이성질체를 N-hexadecyl-L-proline이 코팅된 역상 원심 액체크로마토그래피로써 분리, 분취하였다. 아미노산 이성질체의 용리 및 분리에 영향을 주는 구리(Ⅱ) 농도, pH, 이동상의 유기용매 종류 및 농도, 원심 액체크로마토그래피의 원형 컬럼의 회전속도 등에 대하여 연구하였다. 수 mg의 소수성 아미노산을 분취하였다. 모든 다른 아미노산을 분리 및 분취하려면, 다양한 코팅 리간드에 대하여 연구하여야 한다.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1496-1500
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• 2010

Sibutramine enantiomers were separated successfully by capillary zone electrophoresis using substituted cyclodextrins as chiral selectors. The effects of cyclodextrin concentration, pH, voltage, buffer type, and electrolyte concentration on the migration time and resolution of enantiomers were examined. Separation of sibutramine enantiomers on an unmodified fused silica capillary (total length, 54 cm; effective length, 45 cm) was achieved using a mixed buffer of 20 mM phosphate/10 mM citrate containing either 5 mM methyl-${\beta}$-cyclodextrin (pH 4.3) or 5 mM carboxymethyl-${\beta}$-cyclodextrin (pH 6.5). Samples were injected with a pressure of 50 mbar for 5 s and were detected at a wavelength of 223 nm. The established method showed good precision and accuracy, with intra- and inter-day variations of less than 2.9 and 4.7%, respectively, and recoveries of 95.7 - 103.8%. The stability constants of (R)- and (S)-sibutramine demonstrated that the resolution of sibutramine enantiomers was attributable primarily to the difference in stability constants. When this optimized method was applied to the determination of sibutramine enantiomers in commercial drug formulations, it proved to be economical and convenient, affording sufficient accuracy, precision, and reproducibility as well as sensitivity and selectivity.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권4호
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• pp.357-363
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• 2006

Monolithic molecularly imprinted columns were designed and prepared by an in-situ thermal-initiated copolymerization technique for rapid separation of tryptophan and N- CBZ-phenylalanine enantiomers. The influence of polymerization conditions and separation conditions on the specific molecular recognition ability for enantiomers and diastereomers was investigated. The specious molecular recognition was found to be dependent on the stereo structures and the arrangement of functional groups of the imprinted molecule and the cavities in the molecularly imprinted polymer (MIP). Moreover, hydrogen bonding interactions and hydrophobic interactions played an important role in the retention and separation. Compared to conventional MIP preparation procedures, the present method is very simple, and its macroporous structure has excellent separation properties.

• Natural Product Sciences
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• 제6권1호
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• pp.20-24
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• 2000

The enantiomers of higenamine were directly separated by high performance liquid chromatography using a chiral stationary phase and detected by UV. The R- and S-isomers of higenamine were eluted at the retention time of 22 min and 27 min, respectively. Higenamine was determined to be present as R-(+)-enantiomer not only in the embryo of Nelumbo nucifera, from which the separation of R-(+)-higenamine was reported, but also in various Aconite roots, from which higenamine was separated as optically inert racemic mixtures.

• 약학회지
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• 제29권6호
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• pp.375-379
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• 1985

The gas chromatographic behavior of optically active N-(N-benzoyl-L-valyl)-anilide used as stationary phase is described. N-(N-benzoyl-L-valyl)-anilide has been synthesized with good yield under mild condition via Schotten-Bauman process and coated on the Chromosorb W AW (80-100mesh) for the purpose of enantiomer separation. The behavior of this compound as optically active stationary phase for the separation of the enantiomers of N-TFA-D, L-amino acid isopropyl esters has been examined with respect to the correlation between the separation factors and column temperatures. All amino acid enantiomers examined were eluted within one hour and the elution pattern showed retention times increasing in the order of alanine, valine, leucine, threonine, proline and methionine.

• 약학회지
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• 제30권1호
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• pp.47-50
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• 1986

The enantiomers of five amino acids (alanine, valine, threonine, leucine and phenylalanine) could be separated by gas chromatography with optically active (S)-5-isopropyll-$N^3$-phenyl-2-thiohydantoinic stationary phase, which prepared from L-valine and phenylisothiocyanate. Gas chromatographic separations on methylesterificated and N-trifluoroacetylated amino acids have been conducted in isothermal at several column temperatures (180~190, 200, $210^{\circ}C$). The separation factors were 1.29 (alanine, $190^{\circ}C$), 1.35 (valine, $190^{\circ}C$), 1.33 (threonine, $190^{\circ}C$), 1.17 (leucine, $190^{\circ}C$) and 1.05 (phenylalanine, $190^{\circ}C$) and D-isomers eluted prior to L-isomers in every instance. The result of this experiment shows that this stationary phase can be used for the separation of the other amino acids enantiomers.

• Archives of Pharmacal Research
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• 제22권6호
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• pp.614-618
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• 1999

A reversed-phase high-performace liquid chromatographic method was developed to determine the optical purity of metoprolol enantiomers. The enantiomers were converted to diastereomeric derivatives using (-)-menthyl chloroformate reagent. Separation of the enantiomers as diastereomers was achieved by reversed-phase HPLC within 30 min using Inertsil C8 column. This method allowed determination of 0.05% of either enantiomer in the presence of its stereoisomer and method validation showed adequate linearity over the required range. Owing to the reaction condition during the derivatization with (-)-menthyl chloroformate, the possibility of racemization had to be established. Different ratios of (S)-(-)-metoprolol and (R)-(+)-metoprolol were prepared. Enantiomeric separation of these mixtures took place on a chiralcel OD column or, after derivatization with (-)-menthyl chloroformate, on a C8 column. The results form the these two independent separation systems were compared with trace racemization and were in very good agreement. No racemization was found during the experiment.