Asymmetric synthesis of <small>L</small>-6-hydroxynorleucine from 2-keto-6-hydroxyhexanoic acid using a branched-chain aminotransferase

Seo, Young-Man,Kim, Aran,Bea, Han-Seop,Lee, Sang-Hyeup,Yun, Hyungdon Informa Healthcare 2012 Biocatalysis and biotransformation Vol.30 No.2

<P><SMALL>L</SMALL>-6-Hydroxynorleucine was synthesized from 2-keto-6-hydroxyhexanoic acid using branched-chain aminotransferase from <I>Escherichia coli</I> with <SMALL>L</SMALL>-glutamate as an amino donor. Since the branched-chain aminotransferase was severely inhibited by 2-ketoglutarate, the branched-chain aminotransferase reaction was coupled with aspartate aminotransferase and pyruvate decarboxylase. Aspartate aminotransferase converted the inhibitory 2-ketoglutarate back to <SMALL>L</SMALL>-glutamate by using <SMALL>L</SMALL>-aspartate as an amino donor. On the other hand, pyruvate decarboxylase further shifted the reaction equilibrium towards <SMALL>L</SMALL>-6-hydroxynorleucine through decarboxylation of pyruvate to acetaldehyde. The concerted action of the three enzymes significantly enhanced the yield compared to that of branched-chain aminotransferase alone. In the coupled reaction, 90.2 mM <SMALL>L</SMALL>-6-hydroxynorleucine (> 99% <I>ee</I>) was produced from 100 mM 2-keto-6-hydroxyhexanoic acid, whereas in a single branched-chain aminotransferase reaction only 22.5 mM <SMALL>L</SMALL>-6-hydroxynorleucine (> 99% <I>ee</I>) was produced.</P>

Measurement of Branching Ratio for broad 27-keV Resonance of 19F(n,g)20F Reaction by using Time-of-flight Method with Anti-Compton NaI(Tl) Spectrometer

이삼열 한국방사선학회 2008 한국방사선학회 논문지 Vol.2 No.1

The neutron capture spectrum for the light nuclide was very useful to study the nuclear structure. In the present study, the capture gamma-ray from the 27-keV resonance of 19F(n,g)20F reaction were measured with an anti-Compton NaI(Tl) spectrometer and the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo institute of technology. A neutron Time-of-Flight method was adopted with a 1.5 ns pulsed neutron source by the 7Li(p,n)7Be reaction. In the present experiment, a Teflon((CF2)n) sample was used The sample was disk with a diameter of 90 mm. The thickness of sample was determined so that reasonable counting rates could be obtained and the correction was not so large for the self-shielding and multiple scattering of neutrons in the sample, and was 5mm. The primary gamma-ray transitions were compared with previous measurement of Kenny. The neutron capture spectrum for the light nuclide was very useful to study the nuclear structure. In the present study, the capture gamma-ray from the 27-keV resonance of 19F(n,g)20F reaction were measured with an anti-Compton NaI(Tl) spectrometer and the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo institute of technology. A neutron Time-of-Flight method was adopted with a 1.5 ns pulsed neutron source by the 7Li(p,n)7Be reaction. In the present experiment, a Teflon((CF2)n) sample was used The sample was disk with a diameter of 90 mm. The thickness of sample was determined so that reasonable counting rates could be obtained and the correction was not so large for the self-shielding and multiple scattering of neutrons in the sample, and was 5mm. The primary gamma-ray transitions were compared with previous measurement of Kenny.

Preparation and Characterization of High Molecular Weight Poly(butylene succinate)

Han, Yang-Kyoo,Kim, Sung-Rim,Kim, Jinyeol The Polymer Society of Korea 2002 Macromolecular Research Vol.10 No.2

Poly(butylene succinate) (PBS) prepolymers were prepared by the condensation polymerization of 1,4-butanediol (1,4-BD) and succinic atid (SCA) in the presence of titanium (VI) isoproxide(TPI) catalyst. The PBS prepolymers reacted with 1,4-BD or SCA to obtain hydroxyl or carboxylic acid group terminated PBS. High molecular weight linear or branched PBS was synthesized by a coupling reaction between hydroxyl and carboxylic acid group terminated PBS, or by a branching reaction between carboxylic acid group terminated PBS and glycerol as a branching agent. The weight average molecular weight of the prepared linear or branched PBS was in the range of 100,000-220,000. Both melting point and thermal stability of the high molecular weight linear and branched PBSs were somewhat higher than those of general PBS. From a tensile behavior by Instron test, modulus, tensile strength and elongation at break improved with increase in the molecular weight of the prepared PBS through the coupling or the branching reaction. In particular, the high molecular weight linear PBS had about 2.5 times higher value in modulus than the branched one.

Enzymatic Synthesis of L-tert-Leucine with Branched Chain Aminotransferase

( Young Man Seo ),( Hyung Don Yun ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.10

In this study, we demonstrated the asymmetric synthesis of L-tert-leucine from trimethylpyruvate using branchedchain aminotransferase (BCAT) from Escherichia coli in the presence of L-glutamate as an amino donor. Since BCAT was severely inhibited by 2-ketoglutarate, in order to overcome this here, we developed a BCAT/aspartate aminotransferase (AspAT) and BCAT/AspAT/pyruvate decarboxylase (PDC) coupling reaction. In the BCAT/ AspAT/PDC coupling reaction, 89.2 mM L-tert-leucine (ee >99%) was asymmetrically synthesized from 100 mM trimethylpyruvate.

2′-메칠 및 4′-페닐 측쇄를 가진 새로운 카보사이클릭 뉴크레오사이드의 합성 및 항바이러스 약효검색

양선화,홍준희 대한약학회 2004 약학회지 Vol.48 No.1

In this study; a series of 2',4'-doubly branched carbocyclic nucleosides (8,9,10) were synthesized from simple acyclic ketone derivative as starting material. The installation of the 4'-quaternary carbon needed was carried out using a 〔3,3〕-sigmatropic rearrangement. In addition, the introduction of a methyl group in the 2'-position was accomplished by Grig-nard reaction. Bis-vinyl was successfully cyclized using a Grubbs' catalyst II. The natural bases (adenine, cytosine, uracil) were efficiently coupled with the use of a Pd(0) catalyst. Although all the synthesized compounds were assayed against several viruses, only cytosine analogue 9 showed weak antiviral viral activity (EC$_{50}$=45.4 $\mu$M) against CoxB3 virus.s.

중이온가속기 KoRIA와 천체핵물리학

문창범,한인식,권영관,문준영,이주한,천명기,김용균,박세환,이영욱,하장호,정순찬 한국물리학회 2010 새물리 Vol.60 No.8

We discuss topics of thermonuclear reactions for unstable nuclei in nuclear astrophysics at KoRIA (Korea Rare Isotopes Accelerator) facility, which will be built in the near future. Various experimental methods with rare isotope beams (RIB) have been proposed for understanding the formation of the elements following fusion reactions and neutron captures inside and on the surfaces of stars: hydrogen-helium burning processes CNO cycle and chains rapid proton capture reactions (rp-process) slow neutron capture reactions (s-process) and rapid neutron capture reactions (rprocess). We give special emphasis to obtaining reaction rates for the reactions that create and destroy long-lived nuclei, such as 22Na, 26Al and 44Ti, that are targets for γ-ray line astronomy. We also focus on the r-process by which neutron-rich nuclei with neutron magic numbers of 82 and 126 are synthesized. Our proposal will lead the way to solving key issues in astrophysics: the structure and evolution of stars (neutron stars, pulsars, and black holes) the generation of energy in stars and the synthesis of the elements in stars the structure and formation of the solar system and our galaxy. The KoRIA facility is anticipated to play a leading role in developing and promoting nuclear astrophysics research around the world. 한국에서 계획 중인 중이온가속기시설 KoRIA(Korea Rare Isotope Accelerator)의 활용 분야 중 천체핵물리학과 관련된 연구 주제들을 논하였다. 우리는 여기서 우주에서 관측되는 감마선의 생성, 폭발성 천체들에서 일어나는 수소-헬륨 태움반응과 이에 따른 C·N·O 순환, 철 이상의 양성자 과잉 핵종 합성에 관여되는 빠른 양성자 포획과정(rp-process) 등에 대한 다양한 핵반응 실험들을 제안하였다. 또한 느린중성자포획 과정(s-process)과 빠른중성자포획과정(r-process)에 의한 원소합성에 관여되는 중성자 과잉핵종들의 핵반응들에 관한 연구주제들을 논하였다. 특히 중성자 마법수 N = 82, N = 126을 갖는 초 중성자과잉 핵종들을 중요 연구주제로 삼았다. 여기에서 제안된 연구과제들은 새로운 동위원소들의 발견으로 이어지는 것은 물론 새로운 초중핵의 합성 연구에 필수적인 길잡이로 안내할 것으로 믿는다. KoRIA를 이용한 이러한 천체물리학적 연구들은 별들의 생성과 진화과정, 에너지 원천, 은하 생성과 구조의 규명 연구에 세계적인 성과를 올릴 수 있을 것으로 기대된다.

Structural Characteristics of Novel Branched Oligosaccharides Synthesized by a Maltose Acceptor Reaction with Dextransucrase from Leuconostoc mesenteroides M-12

Seo, Hyun Chang 한국식품영양학회 1997 韓國食品營養學會誌 Vol.10 No.1

효소반응과 부분 산가수분해 결과를 해석하여 Leuconostoc mesenteriodes M-12 덱스트란수크라제 억셉터 반응 산물이 새로운 분지올리고당의 구조를 확인하였다. 분지올리고당 B_4의 구조는6^2-O-α-D-kojibiosylmaltose인 것으로 확인되었으며, 분지올리고당 B_5의 구조는 6^3-O-α-D-kojibiosylpanose였다. 억셉터 반응산물을 덱스트라나제로 분해한 결과 새로운 올리고당인 D_4를 확인할 수 있었다. 억셉터 반응의 산물을 억셉터로 이용한 두 번째 억셉터 반응의 생성물을 덱스트라나제 처리하여 D_4를 얻었는데 덱스트라나제와 글루코아밀라제에 의해 분해되지 않았다. 그 구조는 6^2-O-α-D-kojibiosylisomaltose로 확인되었다. 직선상 또는 분지결합을 가진 d.p. 6이하의 억셉터 반응산물의 생성 패턴도 확인하였다. The structures of novel branched oligosaccharidse synthesized by the acceptor reaction with dextransucrase from Leuconostoc mesenteriodes M-12 were proposed in accordance with the results obtained from enzymatic hydrolysis and a partial acid hydrolysis. The structure of branched oligosaccharide B_4 was shown to be 6^2-O-α-D-kojibiosylmaltose. Branched oligosaccharide B_5 was shown to be 6^3-O-α-D-kojibiosylpanose. By reacting the acceptor reaction products with endodextranase a novel branched oligosaccharide(D_4) coule be produced. D_4 was derived from the result of endodextranase hydrolysis of oligosaccharides synthesized by the second acceptor reaction with dextransucrase and was resistant to endodextranase and glucoamylase. The proposed structure of D_4 was 6^2-O-α-D-kojibiosylisomaltose. Formation pattern of the acceptor reaction products smaller than d.p. 6 with linear or branched linkage was also shown.

Synthesis of Novel Carbovir Analogue

Kim, Ai-hong,Hong, Joon-Hee Korean Chemical Society 2006 Bulletin of the Korean Chemical Society Vol.27 No.7

The synthesis of 4'-phenyl and 1'-methyl doubly branched carbocyclic nucleoside was accomplished from 2-hydroxy acetophenone. The 4'-phenyl group was installed via a [3,3]-sigmatropic rearrangement reaction, and the carbonyl addition of methylmagnesium bromide was used to introduce the 1'-methyl group. Cyclization of divinyl 9 was performed using $2^{nd}$ generation Grubbs catalyst. The coupling of cyclopentenol 12$\alpha$ with 6-chloropurine by Mitsunobu reaction and desilylation was used to synthesize the target nucleoside 15.

B형 간염 표면항원과 표면항체 공존예에서의 HBV-DNA 검출을 위한 분자생물학적 방법 비교

김문정,김현숙,권오헌,한광협 대한임상병리학회 1997 대한임상병리학회지 Vol.17 No.6

Synthesis of Novel 2'-Methyl Carbovir Analogues as Potent Antiviral Agents

홍준희 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.2

In this study, the synthesis procedures of 2'-branched carbovir analogues were accomplished. The introduction of a methyl group in the requisite 2'-position was carried out by the addition of a carbonyl using isopropenyl magnesium bromide. The desired compound, cyclopentenol 10(β), was synthesized via ring-closing metathesis using a second-generation Grubbs’ catalyst. The nucleosidic bases (adenine, cytosine, thymine, uracil, 5-fluorouracil and 5-iodouracil) were efficiently coupled using a Pd (0) catalyst. When the synthesized compounds were examined for their activity against several viruses, including HIV-1, HSV-1, HSV-2 and HCMV, the 5- iodouracil analogue, 23, exhibited significant anti-HCMV activity.