• Advances in materials Research
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• 제2권1호
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• pp.51-64
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• 2013

Enantioselective macromer of trimesic acid was prepared using S(-) menthol with trimesoyl chloride on polyimide (PI) ultrafiltration membrane. The chemical composition of macromer as well as polyimide ultrafiltration membrane was determined by ATR-FTIR Spectroscopy. The optical resolution of chiral alcohols was performed in pressure driven process. The effect of monomer solutions concentration, effect of air-drying time of S(-) menthol solution, effect of reaction time, effect of operating pressure, effect of feed concentration of racemate on the performance of macromer was studied. The synthesised material exhibits separation of chiral alcohols (menthol ~23% and sobrelol ~21%).

• Korean Membrane Journal
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• 제1권1호
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• pp.38-42
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• 1999

Membrane technology can be applied in two ways to produce pure enantiomers. In one case a membrane separation process can be cmbined with an enantiospecific reaction to obtain so-called 'en-antiospecific membrane reacto' These systems are useful to carry out asymmetric synthesis or kinetic resolution and simulatneously separate the produced enantiomer. As for general membrane reactors the result is a more compact system with a higher conversion: in fact removal of a product drives equilibrium-limited reactions towards completion. The other way to apply membrane technology to chiral production is the use of intrinsically enantioselective membranes that are able to distinguish between two isomers favouring preferential transport of only one isomer in absence of reaction. In this paper the current development of chiral membrane processes will be discussed.

• 한국막학회:학술대회논문집
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• 한국막학회 1999년도 The 7th Summer Workshop of the Membrane Society of Korea
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• pp.31-34
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• 1999

Membrane technology can be applied in two ways to produce pure enantiomers. In one case, a membrane separation process can be combined with an enantiospecific reaction to obtain so-called 'enantiospecific membrane reactor'. These systems are useful to carry out asymmetric synthesis or kinetic resolution and simultaneously separate the produced enantiomer. As for general membrane reactors, the result is a were compact system with a higher conversion; in fact, removal of a product drives equilibrium-limited reactions towards completion. The other way to apply membrane technology to chiral production is the use of intrinsically enantioselective membranes that are able to distinguish between two isomers favouring preperential transport of only one isomer in absence of reaction. In This paper, the current development of chiral membrane processes will be discussed.

• Korean Membrane Journal
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• 제5권1호
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• pp.25-30
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• 2003

Chitosan membranes crosslinked with glutaraldehayde that contained chiral environment were prepared. The chitosan membranes were characterized using FTIR and swelling index measurements. Their swelling index in water ranged from 100 to 70%, depending on the crosslinking time. The separation of D- and L-isomers of tryptophan was achieved through a pressure driven membrane separation process, using the self-supporting crosslinked chitosan membranes. The chiral separation performance of the membranes depended strongly on the swelling index of the membranes and the separation conditions such as concentration of feed solutions and different operating pressures. Especially when a chitosan membrane with a swelling index of 70% was used, almost complete optical resolution of D- and L-tryptophan was obtained ; enantiomeric excess (ee %) of 97.92% and flux of 2.26 g/㎡$.$h.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.61-64
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• 2003

Optical resolution of a-amino acid (tryptophan and tyrosine) optical isomers was achieved by a pressure driven membrane separation process, using self-supporting crosslinked membranes base on polysaccharide with different swelling indices that ranged from 100 to 70%. The membranes prepared by casting and drying the polymer solution containing 5wt% acetic acid on an acryl plate followed by crosslinking with glutaraldehyde were characterized using such analytical methods as FTIR and swelling index measurements. On the way of separating the optical isomers, several experimental factors such as the concentration of the feed solutions, operating pressure and temperature, and degree of crosslinking of the membranes have been studied. When the chitosan membranes with 70% of swelling index were used , almost complete optical resolution was obtained; 97.92% of enantiomeric excess (ee %) and 2.26 g/$m^2$ㆍh of flux. The operating pressure and the concentration of feed solutions were respectively 1.0 kgf/$\textrm{cm}^2$ and 0.49 mmol/L.

• 폴리머
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• 제28권4호
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• pp.352-359
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• 2004

트립토판, 타이로신, 페닐알라닌과 같은 라세미 화합물의 광학 분할을 위해 광학 선택성 분리막을 이용한 막 분리법을 이용하였으며, 사용된 분리막 제조를 위해서 막 재료로 알진산나트륨 (sodium alginate)을, 가교제로 글루타르알데하이드 (glutaraldehyde)를 사용하였다. 제조된 막의 구조는 FT-IR을 이용하여 관찰하였고 라세미화합물의 광학 분할 메카니즘을 확인하기 위해서 모델링을 실시하였다. 막의 가교정도, 공급액의 농도, 조작압력, 그리고 공급액의 증류에 따른 막의 투과 특성을 알아보기 위해 여러 가지 변수를 통한 실험을 실시하였으며, 그 결과 막의 가교도와 두께가 증가할수록, 공급액의 농도와 용질의 크기가 감소할수록 즘 더 높은 광학 분할 능을 나타낸다는 것을 발견하였으며 이때의 enantiomeric excess (%ee) 값은 약 77%로 나타났다.

• 한국막학회:학술대회논문집
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• 한국막학회 1998년도 추계 총회 및 학술발표회
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• pp.15-18
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• 1998

Membrane reactors are systems which combine a chemical reactor with a membrane separation process allowing to carry out simultaneously conversion and product separation. The catalyst can be immobilized on the membrane or simply compartmentalized in a reaction space by the membrane. Membrane reactors are today investigated to produce optically pure isomers and/or resolve racemic mixture of enantiomers. The interest towards these systems is due to the increasing demand of enantiomerically pure compounds to be used in the pharmaceutical, food, and agrochemical industries. In fact, enantiomers can have different biological activities, which often influence the efficacy or toxicity of the compound. On the basis of current literature there are basically two schemes on the use of membrane technology to produce enantiomers. In one case, the membrane itseft is intrinsically enantioselective: the membrane is the chiral system which selectively separates the wanted isomer on the basis of its conformation. In the other, a kinetic resolution using an enantiospecific biocatalyst is combined with a membrane separation process; the membrane separates the product from the substrate on the basis of their relative chemical properties (i.e. solubility). This kind of configuration is widely used to carry out kinetic resolutions of low water soluble substrams in biphasic membrane reactors [Giomo, 1995, 1997; Lopez, 1997]. These are systems where enzyme-loaded membranes promote reactions between two separate phases thanks to the properties of enzymes, such as lipases, to catalyse reactions at the org ic/aqueous interface; the two phases are maintained in contact and separated at the membrane level by operating at appropriate transmembrane pressure. A schematic representation of biphasic membrane reactor is shown in figure 1, while an example of enantiospecific reaction and product separation carried out with these systems is reported in figure 2.

• Journal of Microbiology and Biotechnology
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• 제23권3호
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• pp.343-350
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• 2013

(R)-[3,5-Bis(trifluoromethyl)phenyl] ethanol is a key chiral intermediate for the synthesis of aprepitant. In this paper, an efficient synthetic process for (R)-[3,5- bis(trifluoromethyl)phenyl] ethanol was developed via the asymmetric reduction of 3,5-bis(trifluoromethyl) acetophenone, catalyzed by Leifsonia xyli CCTCC M 2010241 cells using isopropanol as the co-substrate for cofactor recycling. Firstly, the substrate and product solubility and cell membrane permeability of biocatalysts were evaluated with different co-substrate additions into the reaction system, in which isopropanol manifested as the best hydrogen donor of coupled NADH regeneration during the bioreduction of 3,5-bis(trifluoromethyl) acetophenone. Subsequently, the optimization of parameters for the bioreduction were undertaken to improve the effectiveness of the process. The determined efficient reaction system contained 200mM of 3,5-bis(trifluoromethyl) acetophenone, 20% (v/v) of isopropanol, and 300 g/l of wet cells. The bioreduction was executed at $30^{\circ}C$ and 200 rpm for 30 h, and 91.8% of product yield with 99.9% of enantiometric excess (e.e.) was obtained. The established bioreduction reaction system could tolerate higher substrate concentrations of 3,5- bis(trifluoromethyl) acetophenone, and afforded a satisfactory yield and excellent product e.e. for the desired (R)-chiral alcohol, thus providing an alternative to the chemical synthesis of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol.

• KSBB Journal
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• 제14권3호
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• pp.291-296
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• 1999

광학활성 에폭사이드는 광학활성 의약품, 농약, 기능성 식품 제조용 핵심 유기중간체로 사용될 수 있다. 광학활성 에폭사이드의 생물공학적 생산 사례로는 diltiazem 합성용 중간체인 methyl trans-3-(4-methoxyphenyl)glycidate를 lipase를 고정화한 중공사막 반응기를 이용하여 생산되고 있으며, 미생물 탈할로겐화반응을 이용하여 광학활성 epichlorohydrin 및 glycidol도 생산되고 있다. 생물공학적으로 광학활성 에폭사이드를 생산하는 방법은 크게 두 가지로 구분할 수 있는데, 알켄 등을 기질로 하여 monooxygenase나 perocidase 등을 이용하여 직접 에폭시화반응을 시키는 방법과 박테리아, 곰팡이, 효모 유래의 미생물 에폭사이드 가수분해효소를 이용하여 라세믹 에폭사이드를 광학분할시켜 얻는 방법이 있다. 특히 에폭사이드 가수분해효소를 이용한 광학활성 에폭사이드 생산은 높은 광학순도를 얻을 수 있으며 일반적으로 라세믹 에폭사이드를 값싸고 쉽게 구할 수 있어 상업화 가능성이 우수하므로 이에 대한 많은 연구개발이 필요하다.