共查询到19条相似文献,搜索用时 125 毫秒
1.
2.
在有机溶剂/缓冲液双相体系中, 利用固定化醋酸杆菌Acetobacter sp.CCTCC M209061细胞高对映体选择性地催化1-(4-甲氧基)-苯基乙醇(MOPE)的不对称氧化反应, 成功地拆分外消旋MOPE得到对映体纯(S)-MOPE. 与游离细胞相比, 固定化细胞催化反应速度有所降低, 但其稳定性(包括操作稳定性、 热稳定性和储藏稳定性)明显提高. 固定化细胞连续使用10批次(每批次12 h)后, 仍能保留其初始催化活性的58%以上, 而游离细胞仅保留约20%的相对活性. 在所考察的不同有机溶剂中, 正己烷不仅能较好地溶解底物, 而且对细胞的生物相容性相对较好, 因而提高了反应底物浓度、 反应初速度、 对映体回收率及残留底物e.e.值, 是反应体系中最适宜的有机相. 该反应的最适宜正己烷体积分数为60%, 辅底物为50 mmol/L丙酮, 底物浓度为40 mmol/L, 缓冲液pH=6.5, 反应温度为30 ℃; 在此条件下, 反应初速度为80.4 μmol/min, 反应12 h后, 对映体回收率和残留底物e.e.值分别为51.0%和99.9%, 明显好于水单相反应体系. 相似文献
3.
手性全碳季碳立体中心的高效构建一直是不对称催化领域的难点和热点.其中,α-全碳季碳非环状醛因具有立体环境拥挤和构象多变性等结构特点,相关不对称合成方法一直发展缓慢.本工作基于手性醛和高烯丙基醇化合物的合成应用重要性,通过Antilla烯丙基化反应,采用2,4,6-三异丙基苯基取代的联萘二酚型手性磷酸催化剂,以较好的产率、立体选择性和选择性系数(最高达到37.0),实现了外消旋α-全碳季碳非环状醛的动力学拆分,为含α-全碳季碳的醛和高烯丙基醇两类手性化合物的合成提供了新思路. 相似文献
4.
5.
华根霉全细胞脂肪酶催化合成生物柴油 总被引:1,自引:0,他引:1
比较了5种不同商品化脂肪酶和自制的华根霉CCTCCM201021全细胞脂肪酶(RCL)催化油脂合成生物柴油的转化效果,结果表明,RCL能有效应用于无溶剂体系催化合成生物柴油.在无溶剂体系中对该酶催化生物柴油的转酯化反应工艺进行优化,考察了甲醇用量、体系含水量、酶的添加量和反应温度对生物柴油收率的影响,使生物柴油最终收率大于86.0%.在有机溶剂体系中选择不同有机溶剂作为助溶剂进行转酯化反应,发现logP值在4.0~4.5的有机溶剂具有较好的转化效果.其中以正庚烷为助溶剂的转酯化反应具有最高的生物柴油收率86.7%.在无溶剂体系中RCL催化转化油酸和模拟高酸价油脂合成脂肪酸甲酯的研究表明,该酶具有很好的催化合成生物柴油的潜力. 相似文献
6.
7.
8.
9.
10.
11.
Aldol condensation of different ketones with various aromatic aldehydes proceeds efficiently in the presence of catalytic amount of perfluoroalkylated-pyridine in a fluorous biphasic system without fluorous solvent, which has prompted various concerns involving cost, solvent leaching, and environmental persistence. The catalyst can be recovered by simple cooling and precipitation and used again. 相似文献
12.
水溶性Rh-BISBIS配合物对阿维菌素催化加氢的研究 总被引:1,自引:0,他引:1
The hydrogenation of avermectin catalyzed by [RhCl(COD)]_2-BISBIS[COD:1,5-cyclooctadiene,BISBIS:sulfonated 1,1'-bis(diphenylphosphino Methyl-2,2'-biphenyl)] in situ in aquenous/organic two-phase system was studied.The influence of various parameters,such as the surfactant concentration,the molar ratio of rhodium to phosphine,the reaction temperature and pressure on this hydrogenation were investigated.The results showed that the hydrogenation activities of diphosphine was higher that of monophosphine. 相似文献
13.
Aromatic hydroxylation catalyzed by toluene 4-monooxygenase in organic solvent/aqueous buffer mixtures 总被引:3,自引:0,他引:3
Toluene 4-monooxygenase is a four-protein component diiron enzyme complex. The enzyme catalyzes the hydroxylation of toluene
to give p-cresol with ∼96% regioselectivity. The performance of the enzyme in two-phase reaction systems consisting of toluene, hexane,
or perfluorohexane and an aqueous buffer was tested. In each of the cosolvent systems, containing up to 93% (v/v) of solvent,
the enzyme was active and exhibited regioselectivity indistinguishable from the aqueous reaction. Using the perfluorohexane/buffer
system, a number of polycyclic aromatic hydrocarbons were oxidized that were not readily oxidized in aqueous buffer. An instability
of the hydroxylase component and a substantial uncoupling of NADH utilization and product formation were observed in reactions
that were continued for longer than ∼3 min. More stable enzyme complexes will be needed for broad applicability of this hydroxylating
system in nonaqueous media. 相似文献
14.
Seventeen inorganic and organic anions, that normally are insufficiently separated via ion chromatography, were completely separated by the addition of an organic solvent to a solution of BGE combined with an adjustment of the apparent pH via CE in combination with indirect UV absorbance detection. Methanol, ethanol, and acetonitrile were examined for their utility in manipulating the selective separation of anions. Methanol and acetonitrile were better modifiers than ethanol at enhancing the resolution of anions comigrating in an aqueous solution of BGE. Methanol was selected as the modifier that provided the largest separation window that could achieve a complete separation of the target analytes. Via the use of methanol, manipulation of the selectivity between inorganic anions and that between inorganic and organic anions was enhanced, but the separation between organic anions remained difficult when only methanol was used. By varying the apparent pH of the BGE in the presence of 10% v/v methanol, however, the separation selectivity between organic anions was substantially improved. Eventually, 7 inorganic and 10 organic anions were simultaneously separated using BGE at a pH of 6.3 in the presence of 10% v/v methanol. 相似文献
15.
Mycelia of Aspergillus oryzae display high enantioselectivity towards (R)-flurbiprofen and can be efficiently used in pure organic solvent for the resolution of (R,S)-flurbiprofen through esterification. The use of the lyophilized mycelia facilitates the separation process so that in one step the two enantiomers of flurbiprofen, which are both valuable for pharmaceutical applications, can be easily separated. The biotransformation can be carried out in different apolar solvents using different primary alcohols as nucleophiles under very mild conditions. 相似文献
16.
Nobuyuki Mase 《Tetrahedron letters》2005,46(18):3213-3216
Chiral phase-transfer catalyzed enantioselective alkylations of tert-butyl glycinate-benzophenone Schiff base were investigated in aqueous media without any organic solvent. Reactions in aqueous media smoothly proceeded to give the desired product in higher yield than under standard liquid-liquid biphasic conditions. In aqueous media the formation of benzophenone, which was caused by in situ hydrolysis of Schiff base, was depressed. 相似文献
17.
The aqueous/organic biphasic hydroformylation of 1‐octene catalyzed by Co2(CO)8/Ph2P(CH2CH2O)nMe, an in situ formed thermoregulated phase‐transfer cobalt catalyst, has been developed. The catalyst activity in this biphasic system was as high as that in the homogeneous system. The yield of oxo‐products was 93% when the reaction was carried out at 180 °C and under 4.0 MPa syngas pressure for 20 h. The catalyst could be easily recovered in the aqueous phase by decanting after the reaction system was cooled, and reused in consecutive reaction without any treatment. The loss of Co in the organic phase was less than 1% on average of five successive runs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
18.
Solid phase extraction (SPE) with appropriate solid sorbents has been commonly used in the routine extraction of organic pollutants in water. The elution of analytes from the solid sorbents normally takes place by organic solvents under an applied vacuum. In this study, a microwave-assisted solvent elution technique was developed for the elution of analytes from C18 membrane disks during microwave irradiation from a microwave extraction system (MES). Several parameters, namely, elution solvent, elution temperature, duration of elution and the volume of solvent which may affect the elution efficiency of microwave-assisted solvent elution (MASE) technique towards organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs), organophosphorus pesticides (OPs), fungicides, herbicides and insecticides from the membrane disk were investigated. Good recoveries above 75% were obtained for most of the organic pollutants using the optimum SPE-MASE technique. The effect of sodium chloride and humic acid on the recoveries on the target analytes were also investigated. 相似文献