• 대한화학회지
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• 제29권3호
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• pp.247-251
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• 1985

네자리 리간드인 ethylenediamine-N,N'-di-S-${\alpha}$-propionic acid (eddp)의 디클로로 코발트(III) 착물을 공기산화법에 의하여 합성하였다. eddp리간드는 코발트(III) 이온에 매우 입체선택적으로 배위하여 ${\Delta}$-S-cis 이성체만을 형성함이 관찰되었다. 합성된 착물의 구조는 원소분석, 적외선 분광분석법, 핵자기 공명 및 흡수스펙트럼으로 확인되었으며 특히 착물의 절대배열은 핵자기공명 스펙트럼으로 확인하였다.

• Archives of Pharmacal Research
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• 제14권4호
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• pp.364-369
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• 1991

The synthesis and regioselective reactions of a chiral allyl sulfide. (S)-(+)-(1-methylpyrrolidin-2-yl)methyl allyl sulfide (MAS, 1) are described. Remarkable ${\alpha}-regioselectivity$ was observed in the alkylation of the carbanion of MAS while 1:3 mixtures of ${\alpha}-and\;{\gamma}-adducts$ were produced in the addition of the MAS anion to aldehydes. However, a dramatic change of the regioselectivity was witnessed when Lewis acids such as $Et_3Al$, $Et_3B$, and $Ti(O^iPr)_4$ were used as additives in the addition reaction. In these cases, ${\alpha}-adducts$ were formed exclusively. A rationale for the change of regioselectivity is provided. And the stereochemical aspect of the addition reaction is also described.

• Bulletin of the Korean Chemical Society
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• 제7권1호
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• pp.66-69
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• 1986

The reaction of potassium trialkoxyborohydrides of varying steric requirements with lithium chloride in tetrahydrofuran(THF) was examined in detail to establish the generality of this synthesis of the corresponding lithium trialkoxyborohydrides. The metal ion exchange reaction between potassium triisopropoxyborohydride and lithium chloride in THF proceeded instantly at room temperature and the corresponding lithium salt was very stable toward disproportionation. However, for R = s-Bu, t-Bu and 2-methylcyclohexyl, with increasing steric requirement, the lithium derivatives were unstable and thus dissociated into $(RO)BH_3^-\;and\; (RO)_4B^-$. The stereoselectivity of lithium triisopropoxyborohydride(LIPBH) in the reduction of representative cyclic ketones was examined and compared with that of the potassium derivative.

• Bulletin of the Korean Chemical Society
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• 제17권10호
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• pp.900-905
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• 1996

Details are described of reaction of carbonyl compounds with diisobutyldialkylaminoalane (DIBAL-NR2; R=Et, i-Bu, Ph) in order to establish their reduction characteristics. The reagents were extremely mild and reduced only aldehydes and ketones effectively in ethyl ether at 25 ℃. The stereoselectivity in the reduction of representative cyclic ketones appeared not so high but quite different from that obtained by DIBAL-H itself. The reagents reduced α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols without any detectable 1,4-reduction products. DIBAL-NR2 also achieved the selective reduction of aldehydes or ketones in the presence of keto or other readily reducible functional group, however the chemoselectivity was less satisfactory than that achieved by diisobutylethoxyalane (DI-BAL-OEt).

• Bulletin of the Korean Chemical Society
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• 제11권4호
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• pp.307-309
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• 1990

The stereoselectivity of the reaction between methyl vinyl ketone dimer, which contains two possible sites of chelation, and zinc borohydride or diisobutylaluminum hydride has been studied in order to illuminate the factors involved in the high levels of asymmetric induction obtained in the bicyclic system. The conditions for the formation of the exo-5,7-dimethyl-6,8-dioxabicyclo[3.2.1]octane are DIBAH reduction of MVK dimer in ether at reflux followed by acidic cyclizatioan, and for the endo isomer are $Zn(BH_4)_2$ reduction with $ZnCl_2$ at $0^{\circ}C.$.

• Bulletin of the Korean Chemical Society
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• 제8권4호
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• pp.313-318
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• 1987

The approximate rate and stoichiometry of the reaction of excess Thexylbromoborane-methyl sulfide, $ThxBHBr{\cdot}SMe_2,$ with selected organic compounds containing representative functional groups under standardized conditions (methylene chloride, $0^{\circ}C)$ were studied in order to characterize the reducing characteristics of the reagent for selective reductions. The selectivity of the reagent was also compared to the selectivity of thexylchloroborane-methyl sulfide. Thexylbromoborane appears to be a much milder and hence more selective reducing agent than thexylchloroborane. The reagent tolerates many organic functionalities. Thus, the reagent shows very little reactivity or no reactivity toward acid chlorides, esters, epoxides, amides, nitro compounds including simple olefins. However, this reagent can reduce aldehydes, ketones, carboxylic acids, nitriles, and sulfoxides. Especially the reagent reduces carboxylic acids including ${\alpha},{\beta}$ -unsaturated ones and nitriles to the corresponding aldehydes. In addition to that, thexylbromoborane shows good stereoselectivity toward cyclic ketones, much better than the chloro-derivative.

• 한국미생물·생명공학회지
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• 제51권4호
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• pp.333-352
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• 2023

Transaminase represents the most important biocatalysts used for the synthesis of chiral amines due to their stereoselectivity. They allow asymmetric synthesis with high yields and enantioselectivity from their corresponding ketones. Due to their environmentally friendly access for the preparation of chiral amines, they have attracted growing attention in recent times. Thus, the production of chiral compounds by transaminase catalysed reactions is considered as an important application in synthetic organic chemistry. Therefore, transaminase is considered to be an important enzyme in the pharmaceutical and chemical industries. ω-Transaminase holds great potential because of its wide substrate specificity thus making it a suitable enzyme to be used at an industrial scale. This review highlights the reaction mechanism, classification, substrate specificity, and biochemical properties. The review also showcases the application of ω-transaminase in organic chemistry with a focus on the production of active pharmaceutical ingredients (APIs).

• 공업화학
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• 제26권1호
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• pp.111-115
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• 2015

두 종류의 새로운 베스타틴(bestatin) 유사체를 $\small{D}$-leucine과 $\small{D}$-valine으로부터 효율적이면서 입체선택적으로 합성하였다. 아미노펩티데이즈 억제제인 베스타틴은 면역조절 효과를 보이며 급성백혈병 치료제로 상품화되어 있다. 주요 중간체인 trans-옥사졸리딘 메틸에스터 2a와 2b는 페닐설포닐나이트로메테인($PhSO_2CH_2NO_2$)과 N-하이드록시 메틸기가 보호기로 도입된 ${\alpha}$-아미노 알데하이드(4a와 4b) 간의 일련의 세 단계 연속반응과 연이은 가오존분해 반응으로부터 20 : 1 이상의 입체선택성으로 합성되었다. 2a와 2b의 가수분해 반응 후에 $\small{L}$-Leu-OMe와의 펩타이드 결합을 통하여 베스타틴의 새로운 유사체인 3a와 3b를 보호기가 도입된 형태로 얻었다. 이소부틸기와 이소프로필기를 갖는 두 종류의 새로운 베스타틴 유사체(1a와 1b)는 해당 ${\alpha}$-아미노알데하이드 4로부터 높은 입체선택성으로 6단계에 걸쳐 각각 51%와 38%의 수율로 합성되었다.

• Journal of Microbiology and Biotechnology
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• 제29권11호
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• pp.1769-1776
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• 2019

Ethyl (S)-3-hydroxy-3-(2-thienyl) propanoate ((S)-HEES) acts as a key chiral intermediate for the blockbuster antidepressant drug duloxetine, which can be achieved via the stereoselective bioreduction of ethyl 3-oxo-3-(2-thienyl) propanoate (KEES) that contains a 3-oxoacyl structure. The sequences of the short-chain dehydrogenase/reductases from Chryseobacterium sp. CA49 were analyzed, and the putative 3-oxoacyl-acyl-carrier-protein reductase, ChKRED12, was able to stereoselectively catalyze the NADPH-dependent reduction to produce (S)-HEES. The reductase activity of ChKRED12 towards other substrates with 3-oxoacyl structure were confirmed with excellent stereoselectivity (>99% enantiomeric excess) in most cases. When coupled with a cofactor recycling system using glucose dehydrogenase, the ChKRED12 was able to catalyze the complete conversion of 100 g/l KEES within 12 h, yielding the enantiopure product with >99% ee, showing a remarkable potential to produce (S)-HEES.

• 대한화학회지
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• 제19권4호
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• pp.218-224
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• 1975

바닥상태에 대한 자기무당착장 상호작용 에너지 이론을 2-치환-아크릴로니트릴과 시클로펜타디엔의 Diels-Alder 반응에 적용하여 반응성과 입체 선택성을 조사하였다. 출발점으로는 $\sigma$전자와 $\pi$전자를 다 고려하는 CNDO/2 MO가 사용되었다. 1차 상호작용 에너지 계산으로 정성적인 반응성이 얻어 졌으며 활성화 에너지 값은 실측치 범위의 것이 계산되었다. 2차 상호작용 에너지 계산으로 얻은 입체 선택성은 치환기에 대하여 모두 endo 선택성을 보여주었다. 비대칭 폐환의 원인을 반응원자의 원잣가 비활성 전자밀도로서 설명하였다.