• Bulletin of the Korean Chemical Society
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• 제8권6호
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• pp.471-475
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• 1987

Benzotriazol-1-yl Diethyl phosphate and benzotriazol-1-yl diphenyl phosphate were conveniently prepared in essentially quantitative yields by the reaction of diethyl chlorophosphate and diphenyl chlorophosphate with equal amounts of 1-hydroxybenzotriazole and triethylamine in tetrahydrofuran at room temperature, respectively. Benzotriazol-1-yl diethylphosphate was effective for the preparation of amides from carboxylic acids amines. Young test and Anderson test for racemization studies using benzotriazol-1-yl diethyl phosphate were investigated and practically no racemization occurred. However, racemization occurred to some extent during coupling of Z-Phe-Val-OH with Pro-OBu. Several dipeptides and tripeptides were prepared without little racemization using benzotriazol-1-yl diethyl phosphate. Benzotriazol-1-yl diphenyl phosphate was less effective than benzotriazol-1-yl diethyl phosphate in terms of the degree of racemization.

• Macromolecular Research
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• 제14권5호
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• pp.510-516
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• 2006

Lactide was produced from oligomeric PLA by back-biting reaction of the OH end groups. For optimization of the reaction conditions, the effects of temperature, pressure, PLA molecular weight, and catalyst type on the lactide synthesis were examined. The fraction of D,L-lactide decreased with increasing temperature. Among the various Sn-based catalysts, the D,L-lactide fraction was maximized when SnO was used. A higher yield with lower racemization was observed at lower pressure. The conversion of PLA was maximized at an oligomeric PLA molecular weight of ca. 1380. The yield of lactide increased but the fraction of D,L-lactide decreased with increasing molecular weight. The highest conversion with the lowest racemization degree was obtained at a catalyst concentration of 0.1 wt%. The lactide was more sensitive to racemization because of the entropic effect.

• 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.

• 대한화학회지
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• 제30권4호
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• pp.377-382
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• 1986

광학활성인 ${\Delta}-[Co(en)_3]^{3+}$ion을 이용하여 라세미체인 $[Co(ox)_3]^{3-}$ 이온을 광학분할한 후 얻어진 ${\bigwedge}-[Co(ox)_3]^{3-}$ 이온의 라세미화를 여러가지 혼합용매 즉, 물-유기용매(유기용매=에탄올, 이소푸로필알코올, 아세톤 및 디옥산)내에서 조사하였다. 라세미화속도는 물<에탄올<이소프로필 알코올<디옥산의 순서로 증가하였고 그 순서는 첨가한 유기용매의 polarizability의 증가순서와 일치하였다. 이상의 결과와 ${\Delta}H^{\neq}$와 ${\Delta}S^{\neq}$를 고려하면 ${\bigwedge}-[Co(ox)_3]^{3-}$의 라세미화메카니즘은 가능한 라세미화메카니즘중 twist메카니즘으로 진행됨을 알 수 있었다.

• BMB Reports
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• 제33권1호
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• pp.82-88
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• 2000

A homologous gene to alanine racemase was cloned from a hyperthermophilic bacterium, Aquifex pyrophilus. The cloned gene encodes a protein of 341 amino acids, which has a significant homology to alanine racemase of Bacillus stearothermophilus, Lactobacillus brevis, and E. coli. When the gene was expressed in Escherichia coli, it produced a 40 kDa protein. The purified protein contains one mole pyridoxal 5-phosphate per one mole of protein, which is essential for catalytic activity of alanine racemase. The purified protein catalyzed racemization of L-alanine to D-alanine, or vice versa, indicating that the cloned gene encoded alanine racemase. It also showed significant racemization activity against L-serine and ${\alpha}-aminobutylic$ acid. The A. pyrophilus alanine racemase showed strong thermostability, and it maintained catalytic activity in the presence of organic solvents.

• Archives of Pharmacal Research
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• 제18권2호
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• pp.69-74
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• 1995

In order to improve physico-chemical properties and to enhance stability of drugs, amino acid salt has been widely adoptd in pharmaceutical synthesis. Acetylsalicylic acid lysinate is one of the widely used analgesics and it is a good example of t5his synthesis. In the case of bacetylsalicylic acid lysinate synthesis, racemization of natrually occurred lysine is esential because the racemic lysine salt of the drug shows better yield, crystallinity and dryness than that of the L-lysine salt. To esatablish a simple, practical and economical process for L-lysine racemization, L-lysine treatments with phosphoric acid and with acetic acid were compared and the optimum conditions for its process and derivatization were investigated by chiral separation methods using GC_MS spectroscopy.

• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.931-933
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• 2004

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.677-679
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• 2013

• Journal of Oral Medicine and Pain
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• 제14권1호
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• pp.43-55
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• 1989

The need of age estimation for identification was increased by complexity of society, and the tooth was used widely for age estimation because of less individual deviation than the other organ. The age estimation using the tooth had several methods. Recently, the one using the racemization of aminoacid in the tooth was admitted more accurate than the other methods, especially in old age. But, this study was not tried in our country, and I would report the result of experiment about age estimation using racemization of dentine. I selected 40-Whole dentine sample from extracted teeth, those were reserved in natural dried condition for 2 weeks~ 1year and calculated the estimation of age from the ratio of D-aminoacid and L-aminoacid (D/L ratio) using gaschromatography and the results were below. 1. The aminoacids showed apparent K/L ratio in dentine were aspartic acid, serine. 2. The aspartic acid showed the highest racemic rate and its rate was 0.0012$\pm$0.0003/yr. 3. The relation between the actual age and K/L ratio was very positive correlation(r+0.954) in the estimation of age using aspartic acid. 4. The deviation between the estimated age using D/L ratio of aspartic acid and actual age was $\pm$3.32.

• KSBB Journal
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• 제19권3호
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• pp.215-220
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• 2004

2-아릴프로피온산 계열의 키랄 의약품의 효소적 dynamic kinetic resolution (DKR) 공정에서 라세미화 염기촉매로 트리 옥틸아민이 지금까지 주로 사용되어 왔으나 반응매질에 녹은 상태로 작용해 회수 및 재사용이 어려웠다. 본 연구에서는 이를 개선하고자 라세미화 반응을 위한 고효율 고체 염기를 탐색해 보았다. 45$^{\circ}C$, 아이소옥탄 내에서 (S)-나프록센 2,2,2-트리플로로에틸 씨오에스터를 기질로 무기 염기류, 염기성음이온교환수지류, resin-bound 염기류 등을 시험한 결과, 약염기성 음이온교환수지인 DIAION WA30을 사용하였을 때 가장 효과적이었다. DIAION WA30의 2차 interconversion constant ( $k_{int}$$^＊/)는 8.6${\times}$$10^{-4}$ m $M^{-1}$ $h^{-1}$이며 동일한 실험조건하에서 수행한 트리옥틸아민 ( $k_{int}$$^＊/ = 2.5${\times}$$10^{-4}$ m $M^{-1}$ $h^{-1}$)에 비해 약 3배가 높았다. 효소 활성에 필수적인 물의 양에 따른 DIAION WA30의 라세미화 효율에 관하여 실험한 결과, 물의 양이 증가할수록 그 효율은 감소하였다. DIAION WA30을 라세미화 촉매로 사용하여 아이소옥탄 내에서 라세믹 나프록센 2,2,2-트리플로로에틸 씨오에스터의 효소적 DKR 반응을 수행해 보았다. 그 결과 DIAION WA30을 사용하지 않은 경우에 비해 반응 전환율과 생성물의 광학 순도는 급격히 향상되었다. 전통적 광학분할 반응의 최대 50%라는 전환율의 제한이 본 연구에서 찾은 DIAION WA30을 첨가함으로써 성공적으로 극복되었다. 또한 고체 염기촉매인 DIAION WA30의 사용은 라세미화 촉매의 회수 및 재사용이 가능하게 해준다.다.다.다.다.다.