• Bulletin of the Korean Chemical Society
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• v.19 no.12
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• pp.1392-1395
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• 1998

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.316-317
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• 1989

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2017-2020
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• 2009

Three complexes, [bis(L-, D- and DL-alaninato)(diaqua)]nickel(II) di-hydrate, were prepared and characterized by X-ray crystallography, gas chromatography, UV-Visible spectroscopy and isothermal calorimetry. Small deviations from the 50:50 distribution of the enantiomers assigned to chiral preferences of the ligands in the complexes were observed. The surprising and unexpected results indicate that complexing alanine with nickel(II) ion alters the racemization rates of D and L isomers of the amino acid. The precipitated complex due to change in pH resulted in preferential precipitation of one isomer with respect to the other. It has been observed that this alternation is ogmented by the long time span which would result in preferential protein forming from the L-isomer. Although the results are bizarre and perplexing, they are fascinating and sound scientifically.

• Bulletin of the Korean Chemical Society
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• v.11 no.3
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• pp.241-244
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• 1990

The photochemistry of 1-Methyl-2-cyclohexenyl aryl ketones (phenyl ketone 7a, p-toluyl ketone 7b, biphenyl ketone 7c and -naphthyl ketone 7d) is reported. The aryl ketone 7a, 7b and 7c undergo photo-racemization with efficiencies of 0.75, 0.79 and 0.76 respectively on direct irradiation. Direct irradiation of the ketone 7d, however, undergoes 1,3-shift with an efficiency of 0.02. Triplet states are responsible for the racemizations and singlet state is responsible for 1,3-shift as in general. The ketone 7a, 7b and 7c are good example of a few ${\beta},{\gamma}$-unsaturated ketones which undergo efficient intersystem crossing on direct irradiation.

• Analytical Science and Technology
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• v.7 no.1
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• pp.41-52
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• 1994

The importance of separation comes from demands on study for exact effect of synthetic drugs and the reactivity of enantiomer in biological system. Racemization rate was measured under the influence of heat, acid, UV-light, enzyme(trypsin) and 6N-HCl at $105^{\circ}C$ on alanine, threonine, isoleucine, lecuine, aspartic acid, methionine, glutamic acid, tyrosine. The method for the identification of overlapped amino acids with GC was developed from the close study of fragmentation pattern with mass spectrometry. With cyclodextrin bonded phase by HPLC, the separation of dansyl amino acid was tested for compartison.

• Analytical Science and Technology
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• v.7 no.1
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• pp.53-64
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• 1994

After establishment of methodology for the separation and quantitation of optical isomer existed in food or biomaterial, the relationship between isomer and nutrient or biological sample was investigated. The optical isomers of standard amino acids and free amino acids were quantitized and the protein was assayed from the Korean bean, pasted bean, soy sauce, gochujang, powderd milk and cataract followed by hydrolysis and dervatization with TFA-IPA for GLC analysis with chirasil val column. Amino acids showing the racemization were alanine, aspartic acid, glutamic acid and phenyl alanine. The most convenient amino acid deducing age and biological activity was aspartic acid. Glutamic acid and phenyl alanine have shown poor resolution with less racemization. The ratio of d-form amino acids was 3~6% for home made pasted bean, about 3% for commerical pasted bean, 2~4% for soy sauce, about 1% for bean, 1~2% for cataract, 1.0~1.5% for powdered milk. The racemization during fermentation process was significant.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.220.3-220.3
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• 2003

Enantiomers of pindolol were prepared by chromatographic method. Racemic pindolol was derivatized with S-(-)-menthyl chloroformate((-)-MCF) forming its diastereomer, R-(+)-pindolol-(-)-MCF and S-(-)-pindolol-(-)-MCF. The diastereomer mixture was then chromatographically resolved to each diastereomer. Each diastereomer was further hydrolyzed with alkali to each enantiomer quantitatively. Racemization was not occurred in this process. Pindolol enantiomers were recovered producing good yield over 30% over all process.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.253.3-254
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• 2002

In boiling aqueous solution, D-amygdalin usually begins to convert into neoamygdalin in 3 min and more than 30% of the initial D-amygdalin is found as neoamygdalin after 30 min. In this report, we establish methods for simple HPLC analysis and the inhibition of D-amygdalin conversion. D-Amygdalin and its conversion product, neoamygdalin, were clearly separated on reverse-phase column chromatography by an optimized eluent of 10mM sodium phosphate buffer (pH 3.8) containing 6% acetonitrile. (omitted)

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.604-607
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• 2000

Preparation for the D-phenylalanine using chemo-enzymatic reaction was investigated. D,L-5-benzylhydantoin was synthesized chemically from L-phenylalanine and converted to N-carbamoyl-D-phenylalanine by the immobilized hydantoinase. The pH and temperature affected the solubility and racemization rate of benzylhydantoin. The optimal temperature and pH of the process were $50^{\circ}C$, 8.5, respectively and the conversion yield hadn't much difference with the hydantoinase content in 10hrs. This produced N-carbamoyl-D-phenylalanine was transformed chemically into D-phenylalanine.

• Archives of Pharmacal Research
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• v.24 no.5
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• pp.402-406
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• 2001

Gas chromatographic method was investigated for the chiral separation of several $\beta$-blockeros(atenolol, betaxolol, bisoprolol, metoprolol and pindolol) using (-)-$\alpa$-methoxy-$\alpa$-(trifluoromethyl)phenylacetyl chloride as a chiral derivatizing agent for amino group. Prior to N-acylation, hydroxyl group was converted into O-silyl ethers by react with N-methyl-H-(taimethylsilyl)trifluoroacetamide. The reaction was selective and rapid and the diasteromeric derivatives were well separated by capillary gas chromatography. (R)-isomers were eluted faster than (S)-isomers when (-)-$\alpa$-methoxy-$\alpa$-(trifluoromethyl)phenylacetyl chloride was used as the chiral derivatizing agent. But in the opposite sequence when (+)-$\alpa$-methoxy-$\alpa$-(trifluoromethyl)phenylacetyl chloride was used. No racemization was found during the reaction.