• KSBB Journal
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• v.9 no.3
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• pp.306-311
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• 1994

Optical resolution of racemic ${\alpha}$-methylbenzylamine was carried out by using Bacillus licheniformis protease in organic media. Enantioselective amidation of racemic amino with an ester as an acyl donor was successfully employed to resolve the racemate. To enhance reaction rate and enantioselectivity, pH-adjustment by lyophilization of enzyme dissolved in buffer, colyophilization with salts or lyoprotectants, selection of solvents and molecular design of esters were investigated. The optimization of the resolution reaction achieved about 30-fold increase in initial reaction rate and about 12-fold increase in enantioselectivity, respectively.

• The Microorganisms and Industry
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• v.17 no.2
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• pp.12-17
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• 1991

미생물학적 물질변환에 대해서는 인류 초기에서부터 효모를 이용하여 빵, 유제품, 알코올, 음료 등의 생산에 이용하여 왔으며, 주로 농업분야 또는 식품 분야에 국한되어 왔다. 1862년 Pasteur에 의해 bacterium xylinum의 순수 배양균주를 사용하여 알코올로부터 초산을 만드는데 응용한 것이 본격적인 시발점으로 보아 무방하겠다. 그 후 acetobacter aceti에 의한 포도당으로부터 gluconic acid 생산과 acetobacter sp.에서의 sorbitol로부터 sorbose 생산 등이 이루어졌고 정통적인 유기합성 방법에 의해 쉽게 만들 수 없는 반응들에 응용되기 시작하였다. 인류 초기의 혼합배양에 의한 물질변환에의 응용과는 달리 순수배양으로 미생물, 식물세포, 혹은 정제된 효소들에 의해 반응이 이루어지게 되었고 순수한 특정 물질에 대한 새로운 순수물질로의 선별적인 수식도 가능해지게 되었다. 특히 발효와 bioconversion의 차이는 racemates의 분리, 비슷한 반응성을 갖는 여러 기들로부터 특정기능을 갖는 기만의 선별적인 수식, 입체 이성체(chiral center)의 제작, 특정 비활성화된 탄소의 기능 등이 bioconversion에서만 수행할 수 있는 독특한 영역으로서 정밀화학분야, energy 분야, 환경오염분야에서의 특히 미래의 관심 기술로 대두되고 있다.

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.770-776
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• 1998

Several ABCH type chiral calix[4]arenes were prepared from monoalkyl calix[4]arenes by treating with various acyl halide, followed by reacting with benzoyl chloride in pyridine. These asymmetrically substituted ABCH type calix[4]arenes are obtained as racemates mixture which are confirmed by the chiral shift reagent in 1H NMR spectra. The molecular and crystal structure of 5-nitro-26-allyloxy-25-benzoyloxy-28-isobutyryloxy-27-hydroxycalix[4]arene 8a has been determined by the X-ray diffraction method. Two independent enantiomeric molecules are crystallized in a 1: 1 racemate mixture. They are in the partial cone conformation in which the benzoyloxy phenyl group is down. There is a bifurcated intramolecular hydrogen bonding involving three functional groups in each molecule.

• YAKHAK HOEJI
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• v.41 no.3
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• pp.277-282
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• 1997

Methamphetamine, which is the most commonly abused drug in Korea, exists in terms of d-, l- isomers and a racemate(dl). d-Methamphetamine is a potent central nervous system stimulant, whereas l-Methamphetamine is sold freely as a nasal decongestant. In addition, methamphetamine appears in different ratios of optical isomers by the clandestine synthesis applied. In this study, enetiomeric separation of methamphetamines was estabilished to distinguish the chirality of methamphetamines trafficked and abused in Korea. A gas chromatograph/mass spectrometer(GC/MS) system equipped with an achiral capillary column is used to isolate the isomers of methamphetamine after (S)-N-(trifluoroacetyl)-l-prolyl(TFP) deravatization.After analyzing 10 illicit methamphetamine powders and 10 positive urine samples, following findings were found: d-Methamphetamine was well resolved from l-Methamphetamine by chromatographic separation of TFP derivatibes on DB-5 with retention time of 11.80 and 11.35 min respectively. The detection of d-Methamphetamine in all 10 powders and 10 urine samples proves that all methamphetamines abused in Korea are illegally manyfactured and administred.

• KSBB Journal
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• v.19 no.1
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• pp.38-41
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• 2004

Enantioselective hydrolysis for the producing chiral epichlorohydrin from its racemic substrate was investigated using epoxide hydrolase activity of Rhodosporidium toruloides SJ-4. The effects of reaction parameters including pH, temperature, initial substrate concentration on initial hydrolysis rate and enantioselectivity were analyzed and optimized. The addition of detergent, Tween 20, enhanced the hydrolysis rate and enantioselectivity. Chiral (R)-epichlorohydrin with high optical purity (＞99% ee) and yield of 25% (theoretically 50% maximum yield) was obtained from its racemate of 20 mM.

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.111-118
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• 1997

The structrue of hydroxy-bisbenzoyloxy-allyloxycalix[4]arene (C45H36O6) has been determined by X-ray crystallography. The crystals are monoclinic, space group P21, unit cell constants a=11.045(3), b=33.545(2) c=10.319(4)Å, β=113.86(2)˚, Z=4, V=3496.0(1.8) Å3, DC=1.28 gcm-3. The intensity data were collected on an Enraf-Noninus CAD-4 Diffractometer with a graphite monochromated Mo-Kα radiation. The structure was solved by direct method and refined by full-matrix least-squares calculations to a final R value of 0.076 for 2945 observed reflections. Two independent enantiomeric molecules are crystallized in a 1:1 racemate mixture. They have the flattened cone conformation with the flattening hydroxy1 pheny1 rings. There is an intramolecular hydrogen bond in both molecules.

• Biomolecules & Therapeutics
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• v.15 no.1
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• pp.40-45
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• 2007

The vascular relaxant effects on isolated rat aorta of amlodipine camsylates (S-, R-enantiomer, and R/S-racemate), were evaluated and compared with that of S-amlodipine besylate. Furthermore, antihypertensive effects were measured in spontaneously hypertensive rat (SHR). The S-amlodipine camsylate concentration-dependently inhibited $Ca^{2+}$-induced contraction of rat aorta with a very slow onset of action (reached its maximum at 3.5h; $ED_{50}:\;1.50\;{\pm}\;0.24$ nM), having a potency 2-fold higher than those of R/S-amlodipine camsylate $(ED_{50}:\;3.36\;{\pm}\;0.91\;nM)$ and similar to those of S-amlodipine besylate $(ED_{50}:\;1.44\;{\pm}\;0.14\;nM)$, whereas the R-amlodipine camsylate has 590-fold lower vasorelaxant activity $(ED_{50}:\;886.4\;{\pm}\;49.7\;nM)$. In SHR, orally administered S-amlodipine camsylate produced a dose-dependent and long-lasting (>>10 h) antihypertensive effect $(ED_{20}:\;0.89\;mg/kg)$, with a potency 2-fold higher than those of R/S-amlodipine camsylate $(ED_{20}:\;1.82\;mg/kg)$ and similar to those of S-amlodipine besylate $(ED_{20}:\;0.71\;mg/kg)$. In contrast, the R-amlodipine camsylate has no effect even-though administrated high concentration 10 mg/kg. These results suggest that S-amlodipine camsylate has the potency and long-lasting antihypertensive activity as single enantiomer drug, and its antihypertensive effect is not significantly different to that of S-amlodipine besylate.

• KSBB Journal
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• v.20 no.4
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• pp.311-316
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• 2005

Epoxide hydrolases (EHs) are versatile biocatalysts for the preparation of chiral epoxides by enantioselective hydrolysis from racemic epoxides. Various microorganisms were identified to possess a EH activity by multiple sequence alignment and analysis of conserved domain sequence from genomic and megaplasmid sequence data. We successfully isolated Gordonia westfalica possessing EH activity from various microbial strains from culture type collections. G. westfalica exhibited (R)-styrene oxide preferred enantioselective hydrolysis activity. Chiral (S)-styrene oxide with high optical purity $(>\;99\%)\;ee)$ and yield of $36.5\%$ was obtained from its racemate using whole-cell of G. westfalica.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.7 no.2
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• pp.147-152
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• 2021

C-11 Radiolabeled amino acid-based radiopharmaceuticals such as [¹¹C]MET for brain tumor PET imaging have limitations due to their short half-life (20 min). F-18 radiolabeled amino acid derivatives have been developed to overcome for the short half-life, one of which is [¹⁸F]FET. Brain tumor imaging using [¹⁸F]FET showed high uptake in tumor region and no non-specific uptake in inflammatory tissue, which was useful in discriminating the difference between inflammation and tumor especially. In this study, [¹⁸F]FET was synthesized using an automatic synthesis module and quality tests were carried out including enantiomeric purity analysis with reference compounds. Radiochemical yield was 50.3 ± 4.9% (n=7, decay-corrected) with molar activity of 76 ± 17 GBq/mmol. The radiochemical purity of >99%. Enantiomeric purity of [¹⁸F]FET using chiral HPLC analysis showed >99%, which was confirmed by co-injection with the L-FET and D-FET authentic standards. [¹⁸F]FET was prepared with high radiochemical yield and molar activity including no racemate mixture.