共查询到18条相似文献,搜索用时 531 毫秒
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利用气相色谱手性分析,对醇腈酶促不对称合成手性氰醇中的pH值、温度、底物浓度和水含量对酶反应速度和非酶反应速度的影响作了研究。结果表明,上述因素对酶反应和非酶反应速度均有显著影响。在水含量较低的非水相酶反应体系中,pH值在4.0以下或反应温度为0-5℃时,非酶反应受到较大程度的抑制,而酶反应仍具有相对较快的反应速度,故可获得高光学纯度的产物。 相似文献
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水/有机溶剂双相中杏仁醇腈酶促不对称合成(R)-苯乙氰醇 总被引:5,自引:1,他引:4
研究了水/有机溶剂双相中来源于杏仁的(R)-醇腈酶催化苯\r\n甲醛与HCN不对称合成(R)-苯乙氰醇,系统探讨了有机溶剂、水相与\r\n有机溶剂相体积比、水相pH值和反应温度对反应速度、转化率和产物光\r\n学纯度的影响.结果表明,上述因素对醇腈酶促不对称合成(R)-苯\r\n乙氰醇反应均有显著影响.异丙醚为该反应最好的有机溶剂,水相与有\r\n机溶剂相体积比以1/2为宜,适宜的pH值为3.4,最佳反应温度为0~\r\n5℃.在该优化反应条件下,反应转化率和产物的光学纯度均高达99%\r\n以上. 相似文献
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水/有机溶剂双相中郁李醇腈酶催化含硅(R)-酮氰醇对映选择性合成 总被引:1,自引:0,他引:1
研究了水/有机溶剂双相中来源于郁李仁的(R)-醇腈酶催化2-三甲基硅-2-乙酮与2-甲基-2-羟基丙腈对映选择性合成(R)-2-三甲基硅-2-羟基丙腈,初步探讨了反应时间、酶粉颗粒大小、底物浓度、底物配比和酶添加量对转氰反应的影响. 结果表明,适宜的反应条件为: 反应时间96 h左右, 酶粉颗粒大小0.3~0.45 mm, 底物2-三甲基硅-2-乙酮浓度14 mmol/L, 底物2-甲基-2-羟基丙腈与2-三甲基硅-2-乙酮摩尔比2:1, 单位体积反应介质中的酶添加量43.5 g/L左右. 在该优化反应条件下,反应平衡转化率和产物的光学纯度(ee值)均可高达99%. 对比研究发现,郁李醇腈酶催化2-三甲基硅-2-乙酮反应在酶促反应初速率、底物转化率和产物光学纯度等方面均显著优于其碳结构类似物3,3-二甲基-2-丁酮. 相似文献
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底物中硅原子对苦杏仁醇腈酶催化不对称转氰反应的影响 总被引:1,自引:0,他引:1
对比研究了不同条件下苦杏仁醇腈酶催化乙酰基三甲基硅烷及其碳结构类似物3,3-二甲基-2-丁酮的转氰反应. 结果表明,苦杏仁醇腈酶催化乙酰基三甲基硅烷转氰反应的初速率及对映体选择性均高于其碳结构类似物在同一条件下的对应值. 动力学研究结果表明,苦杏仁醇腈酶催化乙酰基三甲基硅烷转氰反应的表观动力学参数为Km=27.12 mmol/L和vmax=7.05 mmol/(L·h),活化能为51.92 kJ/mol. 苦杏仁醇腈酶催化3,3-二甲基-2-丁酮转氰反应的表观动力学参数为Km=146.58 mmol/L和vmax=2.52 mmol/(L·h),活化能为75.04 kJ/mol. 根据硅原子的特性及酶反应机理合理解释了实验结果. 相似文献
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氰醇酶制备手性氰醇的研究进展 总被引:4,自引:0,他引:4
手性是自然界的普遍特征 .手性药物的研制和开发 ,是现代制药行业发展的一种必然趋势 ,也是药物研究和开发中急待解决的重大课题 .利用酶的手性合成和制备手性药物中间体是当今国外医药研究的热点 .光学活性氰醇是一类重要的手性合成子 ,它很容易转化为β-氨基醇、α-羟基酸、α-羟基酮等许多手性物质 [1~ 4 ] ,进而合成其它多种光学活性化合物 ,因而在医药、农药等精细化工领域具有广阔的应用前景 ,特别对制备手性药物中间体最具发展潜力 ,它将为手性药物的研制和开发开辟一条新的途径 .手性氰醇的巨大应用价值推动了手性氰醇制备方法的发… 相似文献
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有机溶剂中(R)-醇腈酶催化不对称合成(R)-苯乙醇腈 总被引:3,自引:0,他引:3
研究了来源于杏仁的(R)-醇腈酶在有机溶剂异丙醚中催化苯甲醛与HCN不对称合成(R)-苯乙醇腈,初步探讨了来源于不同杏仁的(R)-醇腈酶的筛选、最适酶量的确定以及底物HCN与苯甲醛的配比、底物浓度、酶的微环境pH和反应温度对不对称合成反应的影响.结果发现,来源于苦杏仁的(R)-醇腈酶优于来源于甜杏仁的(R)-醇腈酶.优化的反应条件为:最适酶量150g/L,HCN与苯甲醛的配比2.5,苯甲醛浓度300mmol/L,酶的微环境pH5.4,反应温度0~5℃.在该优化反应条件下,反应平衡转化率和产物的光学纯度均高达99%以上. 相似文献
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我们从土壤中筛选出一株有自主知识产权的霉菌(白地霉G.38),并发现它有独特的还原性能和优越的反应活性。与啤酒酵母作用相比,催化还原羰基,产物的立体化学上是按anti-Prelog的构型模式进行的。同时我们还开展了羟氰化酶合成光学活性的氰醇化合物的研究,发现和建立了一种适合粗酶作用的微水相工作体系,在工业上有实用前景。并筛选到3个高活性的(R)-氰醇酶源。 相似文献
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不对称Reformatsky反应的研究 总被引:2,自引:0,他引:2
分别将催化计量和化学计量的(1R, 2S)或(1S, 2R)-2-氨基-1,2-二苯基乙醇衍生的手性氨基醇配体1应用于催化不对称Reformatsky反应, 研究了手性配体的结构及其用量与反应对映选择性的关系, 溶剂和底物改变对e.e.值的影响; 并设计与研究了双手性体系, 使该反应在催化量(25mol%)手性配体的作用下, 得到中等对映选择性; 另外, 还比较了不同的实验方法对反应的对映选择性的影响, 提出了手性催化循环机理和反应过渡态模型, 能较好地解释一系列实验事实。 相似文献
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Sen Lin LIU Min Hua ZONG Shun Rong HUANG 《中国化学快报》2005,16(10):1317-1320
The synthesis of optically active (R)- and (S)-2-trimethylsilyl-2-hydroxyl propionitrile by enantioselective transcyanation of acetyltrimethylsilane with acetone cyanohydrin was successfully carded out using defatted plum, loquat , peach, almond or apple seed meals as (R)-oxynitrilase source and using Manihot esculenta leaves as (S)-oxynitrilase source in a biphasic system with good conversion and high enantiomeric excess. Comparative study demonstrated that silicon atom in substrate showed great effect on the reaction and due to the unique characteristics of silicon atom, both the substrate conversion and the product e.e. of the transcyanation of acetyltrimethylsilane were much higher than those of its carbon counterpart 3,3-dimethyl-2-butanone for all examined oxynitrilases. 相似文献
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Po-Yuan Chen Hsing-Ming Chen Michael Y. Chiang You-Feng Wang Sie-Rong Li Tzu-Pin Wang Eng-Chi Wang 《Tetrahedron》2012,68(14):3030-3036
A novel synthesis of substituted 3,4-dihydroisoquinolin-1(2H)-ones is described. o-Oxiranylmethylbenzonitriles, prepared from isovanillin via five synthetic steps, were treated with NaCN/tetra-n-butylammonium bromide (TBAB) to yield 3,4-dihydroisoquinolin-1(2H)-ones in good yields. This one pot reaction demonstrates the novel and chemoselective nature of ring-opening of epoxide by cyanide to generate an iminoisochroman ring via cyclization, again ring-opening by cyanide to generate a Michael acceptor and a donor, and ring re-cyclization through an intramolecular conjugate addition. The detailed mechanism is also rationally proposed. 相似文献
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Erich Hochuli 《Helvetica chimica acta》1983,66(2):489-493
A Rapid Purification of D -Oxynitrilase from Almond Meal by Affinity Chromatography Oxynitrilase from almond meal is capable of catalyzing the stereospecific addition of cyanide to a variety of aldehydes. Thus, the enzyme is potentially useful in the synthesis of optically active cyanohydrins on a preparative scale [1]. As the currently available purification procedures for this enzyme [2] are rather tedious, we have elaborated a simple and rapid procedure based on affinity chromatography. An inhibitor for the enzyme, methyl p-(3-aminopropoxy)benzoate (4) , has been synthesized and attached covalently to Sepharose 4B as a solid matrix (5) . With this affinity gel it was possible to prepare the D -oxynitrilase in a simple procedure with high yields. 相似文献
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[Reaction: see text] The (R)-oxynitrilase from almonds was immobilized as a cross-linked enzyme aggregate (CLEA) via precipitation with 1,2-dimethoxyethane and subsequent cross-linking using glutaraldehyde. The resulting preparation was a highly effective hydrocyanation catalyst under microaqueous conditions, which suppress the nonenzymatic background reaction. The beneficial effect of these latter conditions on the hydrocyanation of slow-reacting aldehydes is demonstrated. The oxynitrilase CLEA was recycled 10 times without loss of activity. 相似文献
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Photoreactions of 4-nitroanisole and the 2-halo-4-nitroanisoles (halogen = F, Cl, Br, I) with NaCN have been investigated. 4-Nitroanisole gave a novel, stable nitronate ion adduct (74%) with cyanide. For the five compounds, we report product distributions, Stern-Volmer kinetic plots, triplet lifetimes, and triplet yields, which afford rate constants for attack by the cyanide ion. Cyanide attack on the fluoride is diffusion controlled; the relative rates for attack at F, Cl, Br, and I are 27:2:2:1, respectively. 相似文献
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A capillary electrophoresis microchip is used to selectively and sensitively monitor cyanide levels in both vapor (HCN((g))) and aqueous (NaCN in drinking water) phases. Laser-induced fluorescence detection is applied using a violet diode laser to monitor the fluorescent isoindole derivative formed by the reaction of cyanide with 2,3-naphthalenedicarboxaldehyde (NDA) and taurine. Air sampling of hydrogen cyanide is achieved using a miniature impinger (2 mL), giving collection efficiencies as high as 79% for a sampling rate of 1.0 L/min and a 10 s sampling time (relative standard deviation RSD: 2.7% for n = 5). Following the addition of NDA and taurine to either the vapor phase impinger sample or an aqueous drinking water sample, the NDA/cyanide derivative can be detected in just over 40 s on the microchip, giving a detection limit of 0.56 microg/L and a linear dynamic range from 0.56 microg/L-2.4 mg/L. The detection limit for hydrogen cyanide in air was determined to be 2.3 ppb (mole%). On-chip derivatization of cyanide by NDA was successful, although a 50% decrease in signal intensity was observed due to insufficient time for completion of the reaction on the microchip. A number of different interferents were examined, and only iron(II) and chlorine showed any interference due to their capability for masking the presence of cyanide by reacting with free cyanide in solution. 相似文献
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The benzil-cyanide reaction is a cyanide-specific reaction that has been exploited to produce a colorimetric indicator for this toxic anion. This was done by producing a pi-extended analogue of benzil, 7, which is soluble in a 70:30 (v/v) mixture of methanol-water. In this medium, dilute solutions of 7 are yellow but produce colorless products when exposed to low concentrations of cyanide anion (> or = 1.7 microM; added as an aqueous NaCN solution), but no other common anions (e.g., OH(-), F(-), N3(-), benzoate(-), and H2PO4(-)). On the basis of these observations and supporting mechanistic analyses, it is concluded that the modified benzil system 7 is a promising cyanide anion indicator that is attractive in terms of its selectivity, ease-of-use, water compatibility, and the low, naked-eye discernible cyanide detection limit it provides. 相似文献