共查询到18条相似文献,搜索用时 203 毫秒
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手性硼酸酯介入的不对称合成3† (R)-或(S)-1,1'-联-2-萘酚硼酸-(S)-脯氨酸酐促进的前手性亚胺的不对称硼烷还原 总被引:1,自引:0,他引:1
手性螺硼酸酯(R)-或(S)-1,1'-联-2-萘酚硼酸-(S)-脯氨酸酐[(R,S)-1或(S,S)-1]对前手性亚胺硼烷还原的不对称催化活性被观察到. 在(R,S)-1或 (S,S)-1存在下, 由前手性二烷基酮或烷基苯酮与苯胺缩合生成的前手性亚胺在THF中被硼烷还原, 高产率地给出手性仲胺, 其对映体纯度高达74% ee. 其中, 三种手性仲胺[N-(2-戊基)苯胺, N-(3-甲基-2-丁基)苯胺和N-(4-甲基-2-戊基)苯胺]系首次合成. 相似文献
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采用改性Ultrastable-Y分子筛固定化P. expansum PED-03脂肪酶(PEL), 利用固定化PEL在微水相中对(R,S)-2-辛醇进行拆分. 结果表明, 改性Ultrastable-Y分子筛固定化PEL所催化的拆分反应的转化率(c)和对映体过量值(e.e.)以及对映体选择性(E)均得到大幅度提高. 介质类型和体系含水量对酶促拆分反应有较大的影响. 在以正己烷为溶剂, 含水量为0.8%的体系中, 于50 ℃反应24 h的转化率(c)可达到理论值的97.68%, 对映体过量值(e.e.)可达到98.75%. 改性Ultrastable-Y分子筛固定化PEL催化效率高、立体选择性强, 且催化性能稳定, 在(R,S)-2-辛醇的酶法拆分方面具有良好的应用前景. 相似文献
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(S)-和(R)-盐酸氟西汀的不对称合成 总被引:2,自引:0,他引:2
盐酸氟西汀是一种临床广泛使用的非三环类抗抑郁药, 本工作介绍了一种不对称合成(S)-和(R)-盐酸氟西汀的方法. 以自制的手性噁唑硼烷为催化剂, 将起始原料β-氯苯丙酮不对称催化氢化还原成(S)-或(R)-手性醇, 这一步的化学收率和光学收率都较高. 然后再经两步, (S)-和(R)-手性醇转化为(S)-和(R)-盐酸氟西汀. 整个工艺只需三步, 总收率为66.5%, 盐酸氟西汀对映体的ee值可达98.6%. 还考察了反应温度、溶剂、催化剂的量等因素对β-氯苯丙酮的不对称氢化还原的化学产率和光学收率的影响. 相似文献
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(S)-和(R)-普萘洛尔的不对称合成 总被引:3,自引:0,他引:3
普萘洛尔是一种临床上广泛使用的β受体阻断剂, 介绍了一种不对称合成(S)-和(R)-普萘洛尔的方法. 以手性Salen-CoIII催化剂水解动力学拆分外消旋环氧氯丙烷得到高光学纯度的(S)-环氧氯丙烷和(R)-3-氯-1,2-丙二醇, 以(S)-环氧氯丙烷为手性原料先水解得(S)-3-氯-1,2-丙二醇, 其与1-萘酚反应得(S)-3-(1-萘基)-丙烷-1,2-二醇, 再与氯化亚砜反应得环状亚硫酸酯, 最后和异丙胺作用得(S)-普萘洛尔, 总收率80.9%, 光学纯度大于99%; 而同样以(S)-环氧氯丙烷为手性原料直接与1-萘酚反应得(2R)-3-(1-萘氧基)-1,2-环氧丙烷, 再与异丙胺作用得(R)-普萘洛尔, 总收率74.5%, 光学纯度大于99%. 相似文献
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将以烯烃为原料通过Sharpless不对称双羟化等多步反应合成的8种手性β-氨基醇, 作为有机小分子催化剂, 用于催化α,β-不饱和酮的不对称环氧化反应.考察了影响对映选择性的催化剂结构、催化剂用量、氧化剂种类、溶剂、反应温度等因素.结果表明, 当催化剂用量为30 mol%、氧化剂为TBHP(叔丁基过氧化氢)、正己烷溶剂、在室温下、以(1S,2R)-(+)-1,2-二苯基-2-甲氨基乙醇(3)作催化剂时, 所得环氧化物的对映体过量最高为70% ee, 产率最高为84%. 相似文献
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The lipase from Penicillium expansum PED-03 (PEL) was immobilized onto modified ultrastable-Y (USY) molecular sieve and the resolution of (R, S)-2-octanol was carried out in a bioreactor in nonaqueous media by the immobilized lipase. It was found that the conversion
rate, enantiomeric excess (ee) value, and enantioselectivity (E) value of the resolution catalyzed by PEL immobilized on modified USY molecular sieve were much higher than those of the
reaction catalyzed by free PEL and PEL immobilized on other supports. Immobilized on modified USY molecular sieve, the PEL
exhibited obvious activity within a wider pH range and at a much higher temperature and showed a markedly enhanced stability
against thermal inactivation, by which the suitable pH of the buffer used for immobilization could be “memorized.” The conversion
rate of the reaction catalyzed by PEL immobilized on modified USY molecular sieve reached 48.84%, with excellent enantio-selectivity
(avarege E value of eight batches >460) in nonaqueous media at “memorial” pH 9.5, 50°C for 24 h, demonstrating a good application potential
in the production of optically pure (R, S)-2-octanol. 相似文献
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报道了配合物RuCl2(BISBI)[(R,R)-DPEN] [BISBI=2,2'-二(二苯膦亚甲基)-1,1'-联苯, DPEN=1,2-二苯基乙二胺]的合成和表征, 并研究了其在苯乙酮不对称加氢反应中的催化性能. 考察了底物/催化剂物质的量比、碱浓度、反应温度和氢气压力等对催化活性和对映选择性的影响, 在苯乙酮/KOH/催化剂的物质的量比为30000∶250∶1, 氢气压力为2 MPa, 反应温度为35 ℃时, 苯乙酮的转化率和生成α-苯乙醇的对映选择性分别达到了100%和65% ee. 相似文献
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Microorganisms producing lipase were isolated from soil and sewage samples and screened for enantioselective resolution of
(R,S)-methyl mandelate to (R)-mandelic acid. A strain designated as GXU56 was obtained and identified as Burkholderia sp. Preparing immobilized GXU56 lipase by simple adsorption on octyl sepharose CL-4B, the optimum temperature was shifted
from 40 °C (free lipase) to 50 °C (immobilized lipase), and the optimum pH was shifted from 8.0 (free lipase) to 7.2 (immobilized
lipase). The immobilized enzyme displayed excellent stability in the pH range of 5.0–8.0, at the temperatures below 50 °C
and in organic solvents compared with free enzyme. Enantioselectivity ratio for (R)-mandelic acid (E) was dramatically improved from 29.2 to more than 300 by applying immobilized lipase in the resolution of (R,S)-methyl mandelate. After five cycles of use of immobilized lipase, conversion and enantiomeric excess of (R)-mandelic acid were 34.5% and 98.5%, respectively, with enantioselectivity ratio for (R)-mandelic acid (E) of 230. Thus, octyl-sepharose-immobilized GXU56 lipase can be used as a bio-resolution reagent for producing (R)-mandelic acid. 相似文献
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有机相酶催化拆分制备(S)-2-氯-1-(2-噻吩)-乙醇 总被引:1,自引:0,他引:1
首次在有机相中对酶催化条件下的2-氯-1-(2-噻吩)-乙醇的反应进行了研究. 通过对不同来源酶的筛选, 找到了Novozym 435和Alcaligenes sp两种选择性较好的酶, 它们均对该反应具有较高的选择性和较快的反应速度, 在此基础上进一步通过对溶剂、温度、摇床转速以及酶用量的筛选, 确定了能够有效拆分2-氯-1-(2-噻吩)-乙醇的较佳反应条件. 当温度35 ℃, 酶量10 mg/mL, 反应72.5 h, 产物的ee值为98.5%时收率为48.6%. 相似文献
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研究了一种化学不对称合成盐酸(R)-沙丁胺醇的方法. 以自制的手性龙脑基β-二酮铁络合物为催化剂催化起始原料3-乙酰氧基甲基-4-乙酰氧基苯乙烯(1)的不对称环氧化, 得到(R)-3-乙酰氧基甲基-4-乙酰氧基苯基环氧乙烷(2), 这一步的化学收率和光学收率都较高. 然后环氧化合物2与叔丁胺发生开环反应, 再与盐酸成盐即制得盐酸(R)-沙丁胺醇. 合成盐酸(R)-沙丁胺醇只需两步, 总收率为68%. 还考察了反应温度、催化剂种类、催化剂的量等因素对3-乙酰氧基甲基-4-乙酰氧基苯乙烯(1)的不对称环氧化的化学产率和光学收率的影响. 相似文献
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Er-na Xun Xiao-li Lv Wei Kang Jia-xin Wang Hong Zhang Lei Wang Zhi Wang 《Applied biochemistry and biotechnology》2012,168(3):697-707
The lipase from Pseudomonas fluorescens (Lipase AK, AKL) was immobilized onto the magnetic Fe3O4 nanoparticles via hydrophobic interaction. Enzyme loading and immobilization yield were determined as 21.4?±?0.5?mg/g and 49.2?±?1.8?%, respectively. The immobilized AKL was successfully used for resolution of 2-octanol with vinyl acetate used as acyl donor. Effects of organic solvent, water activity, substrate ratio, and temperature were investigated. Under the optimum conditions, the preferred isomer for AKL is the (R)-2-octanol and the highest enantioselectivity (E?=?71.5?±?2.2) was obtained with a higher enzyme activity (0.197?±?0.01???mol/mg/min). The results also showed that the immobilized lipase could be easily separated from reaction media by the magnetic steel and remained 89?% of its initial activity as well as the nearly unchanged enantioselectivity after five consecutive cycles, indicating a high stability in practical operation. 相似文献
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H. Yang S. G. Cao S. P. Han Z. L. Huang T. S. Yang J. L. Xu 《Applied biochemistry and biotechnology》1996,59(2):177-186
Stereoselective esterification of(R, S) 2-octanol with octanoic acid catalyzed byCandida Sp lipase (CSL) was carried out in cyclohexane. We have studied the effects of factors, such as temperature and the microenvironment
of lipase, on this reaction. The results showed that CSL favoredR enantiomer of(R, S) 2-octanol, and that the esterification activity and stereoselectivity of the lipase were dependent on these factors. The
higher the temperature, the greater the esterification activity of CSL. A slight increase in stereoselectivity can be seen
with temperature decrease. The optimal range of pH value for this reaction was 4.9–6.2. When the salt concentration was between
0 and 0.05 mol/L, CSL showed high activity. The salt concentration in the reaction system and the pH value at which CSL powder
was prepared from the aqueous solution had no evident effect on the stereoselectivity of CSL.
The optimal range of the water content in the reaction system was 0.4–1.6%. The esterification activity and the stereoselectivity
of CSL were enhanced 1.4-fold and 2.0-fold, respectively, by immediately removing the produced water. (S) 2-octanol with 95.2% enantiomeric excess (ee) was prepared. Based on these results, we have discussed why that all these
factors affected this reaction. 相似文献
18.
ChaoFen Yang HeYan Jiang Jian Feng HaiYan Fu RuiXiang Li Hua Chen XianJun Li 《Journal of molecular catalysis. A, Chemical》2009,300(1-2):98-102
A series of silica (SiO2) supported iridium catalysts stabilized by cinchona alkaloids was prepared and applied in the heterogeneous asymmetric hydrogenation of acetophenone. Cinchona alkaloids exhibited a marked ability to stabilize and disperse the Ir particles. In the presence of (1S,2S)-diphenylethylenediamine ((1S,2S)-DPEN)) as chiral modifier, the cinchonidine (CD) stabilized catalyst 5%Ir/2CD-SiO2 exhibited excellent catalytic performance in the asymmetric hydrogenation of acetophenone in MeOH. Under the optimum conditions, the ee value of (R)-phenylethanol achieved 79.8% and no other product was produced, a higher enantioselectivity than that reported up to now for acetophenone hydrogenation catalyzed by the supported metal catalysts modified by chiral reagents. In particular, a synergistic effect between (1S,2S)-DPEN and CD was observed, which significantly accelerated the reaction rate and enhanced the enantioselectivity. The catalyst can be reused several times without a significant loss of activity and enantioselectivity. 相似文献