脂肪酶催化二次动力学拆分制备高光学纯度(S)-萘普生

设计了一种利用立体选择性相反的两种脂肪酶催化二次动力学拆分,由外消旋萘普生甲酯制备高光学纯度(S)-萘普生的方法。理论曲线预测,与简单的酶促动力学拆分反应相比,二次动力学拆分可以明显提高高光学纯度产物的产率.根据几种脂肪酶在微水/异辛烷双液相反应体系中不对称水解萘普生甲酯的立体选择性和对映体比率(E),首先选用R选择性的固定化南极假丝酵母脂肪酶(Novozym 435)对外消旋萘普生甲酯进行第一次拆分,然后选用S选择性的柱状假丝酵母脂肪酶(CRL)对S过量的剩余底物萘普生甲酯在同样的反应体系中进行第二次拆分.该二次拆分反应对映体过量值为96.8%的(S)-萘普生产率达19.9%.     

水饱和离子液体中脂肪酶催化萘普生甲酯对映选择性水解

 对比研究了水饱和异辛烷和水饱和离子液体1-正丁基-3甲基咪唑六氟磷酸盐([bmim]PF6)中脂肪酶催化萘普生甲酯不对称水解反应. 结果表明,由于离子液体[bmim]PF6同时具有极性和疏水性,因而成为萘普生甲酯不对称水解反应的理想介质. 与水饱和异辛烷相比,水饱和离子液体不仅明显降低了水解反应的平衡常数(K),增大了对映体比率(E),从而有效提高了水解反应的平衡转化率(ceq)和产物的对映体过量值(eep),而且由于离子液体对另一产物甲醇的溶解度高,还明显地提高了脂肪酶的操作稳定性.     

SBA-15固定化脂肪酶催化拆分萘普生甲酯水解反应

利用吸附法将柱状假丝酵母菌脂肪酶(Candida rugosa lipase,CRL)固定于SBA-15介孔分子筛上,在搅拌槽反应体系中催化拆分外消旋萘普生甲酯的水解反应,获得了光学纯对映体(S)-萘普生,考察了SBA-15性能和酶固定量对初始反应速率、产量、转化率、对映体过剩(eep)和对映体选择性(E)的影响.结果...     

有机溶剂-水双液相体系脂肪酶不对称水解合成S-(+)-萘普生

采用有机溶剂－水双液相体系作为反应介质，并用键合有—Ｃ６Ｈ５的无定型多孔硅胶作为分散剂增大两相间的接触面，用圆柱状假丝酵母脂肪酶对萘普生甲酯进行不对称水解．考察了酶浓度、体系ｐＨ值、温度、分散剂对反应的影响．当转化率为２４．３％时，产品萘普生的对映体过量值（ｅｅ）为９４．９％，剩余底物萘普生甲酯的对映体过量值（ｅｅ）为３０．５％，当以异辛烷作为有机相时，该体系酶催化水解的对映体比率（Ｅ）约为５０．     

有机溶剂—水以液相体系脂肪酶不对称水解合成S—（＋）—萘普生

采用有机溶剂－水双液相体系作为反应介质，并用键合有一Ｃ６Ｈ５的无定型多孔硅胶作为分散在两相间的接触面。用圆柱状假丝酵母脂肪酶对萘普生甲酯进行不对称水解，考察了酶浓度、体系ＰＨ值、温度、分散剂对反应的影响，当转化率为２４．３％时，产品萘普生的对映体守量值为９４．９％，剩余底物萘普生甲酯的对映体过量值为３０．５％，当以异辛烷作为有机相时，该体系酶催化水解的对映体比率约为５０。     

CSTR和批式反应器中酶法拆分萘普生的比较

比较了批式反应器和连续流动搅拌反应器中酶动力学拆分萘普生的不同之处。从宏观反应器平衡角度,推导出了在ＣＳＴＲ中不同于在批式反应器中的酶立体选择性,产物对映体过量值和反应转化率的定量关系式,并通过脂肪酶催化的萘一甲酯的不对称水解反应得到了证实。     

底物,水量对脂肪酶不对称拆分萘普生的影响

选择了一种便于底物－产物分离的微水－有机两相体系,将对Ｓ－（＋＿萘普生酯有高度对映体选择性的ＣＣＬ脂肪酶固定于硅藻土上。合成了了一种能提高酶催化反应速度的激活的酯－萘普生氯乙酯。     

膜反应器中萘普生甲酯的动态拆分

在碱催化连续原位消旋条件下,利用CRL脂肪酶（Candida rugosa lipase）催化的萘普生甲酯立体选择性水解反应。动态拆分制备（S）－普生。使用硫水硅橡胶膜隔离生物催化拆分反应和碱催化消旋反应,解决了常规动态拆分反应中生物催化剂难以承受原位化学消旋苛刻反应条件的难题。为了利于从水－有机溶剂乳化体系中分离产物和克服产物抑制,将亲水半透膜引入搅拌罐反应器,在该膜反应器中进行动态拆分反应。当转化率超过60％时,产物（S）－萘普生的对映体过量值（eep)仍在96％以上,在反应过程中还发现CRL脂肪酶同工酶的转化。     

PVP-PdCl2-CuCl2/PPh3体系催化α-（6’-甲氧基-2’-萘基）乙醇羰化反应研究

首次用高分子负载型双金属催化剂PVP-PdCl2-CuCl2/PPh3体系催化α-（6’-甲氧基-2’-萘基）乙醇与一氧化碳及甲醇进行羰化反应制备萘普生甲酯, 分别对温度、压力、时间、 P/Pd比等影响因素进行了考察, 在反应条件为100 ℃、 16～20 h、 CO压力 4.0 MPa、 P/Pd=3时, 转化率可达97.4%, 异正比为14.4. 在同样条件下制备萘普生乙酯及萘普生异丙酯, 转化率及选择性均有明显下降. 另外, 该催化剂体系也可催化其它类型α-芳基乙醇的羰化反应.     

萘普生及其衍生物的手性固定相法直接拆分机理

用不同的酰氯化合物与萘普生反应,制备了一系列萘普生衍生物。在正相色谱条件下,对萘普生及其衍生物系列在(R,R)-Whelk-O 1手性固定相(chiral stationary phase,CSP)上进行了对映体拆分研究。实验考察了流动相组成、分离温度等因素对手性分离的影响,并根据相应热力学参数对萘普生及其衍生物在该手性固定相上的手性识别机理进行了初步探讨。研究结果表明:萘普生及其衍生物在Whelk-O 1 CSP上的对映体分离有着与一般正相色谱明显不同的特征,其分离因子α值与流动相组成关系曲线出现了峰值,且分离因子极大值所对应的流动相组成分别为极性较大的20%(V/V,下同)异丙醇/正己烷混合溶剂体系和40%异丙醇/正己烷混合溶剂体系。     

A parametric study on biphasic medium conditions for the enantioselective production of naproxen by <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase

A parametric study to increase the enantioselectivity of Candida rugosa lipase (CRL) toward S-Naproxen production by the hydrolysis of racemic Naproxen methyl ester in an aqueous-organic biphasic batch system was carried out. Effects of organic solvent type, aqueous phase/organic solvent volume ratio, agitation rate, concentrations of the substrate and the enzyme, pH of the aqueous phase, and temperature on the en antiomeric excess for the product (ee_p), on the enantiomeric ratio (E) and on the conversion (x) were evaluated. Employing isooctane as the solvent resulted in higher ee_p, E, and x than those obtained in hexane, cyclohexane, and toluene. The higher the volume ratio of aqueous phase/organic solvent employed, the higher the conversion and enantioselectivity achieved. The increase in agitation rate increased the hydrolysis rate. Higher concentration of racemic Naproxen methyl ester than 10 mg/mL decreased both the conversion and enantioselectivity. The increase in crude CRL concentration resulted in enhancement of x, but the decrease of fee_p and E. Acidic pH led to higher conversion and enantioselectivity than the medium and alkaline pH values. A further increase in temperature to over 45°C decreased the conversion and enantioselectivity. The highest enantiomeric ratio achieved in the S-Naproxen production was E=171.1, with x=49.8% and ee_p=95.7%.     

Enhancement of the Activity and Enantioselectivity of Lipase by Sol–Gel Encapsulation Immobilization onto β-cyclodextrin-Based Polymer

Candida rugosa lipase was encapsulated within a chemically inert sol–gel support prepared by polycondensation with tetraethoxysilane and octyltriethoxysilane in the presence of β-cyclodextrin-based polymer. The catalytic activity of the encapsulated lipases was evaluated both in the hydrolysis of p-nitrophenylpalmitate and the enantioselective hydrolysis of racemic Naproxen methyl ester. It has been observed that the percent activity yield of the encapsulated lipase was 65 U/g, which is 7.5 times higher than that of the covalently immobilized lipase. The β-cyclodextrin-based encapsulated lipases had higher conversion and enantioselectivity compared with covalently immobilized lipase. The study confirms an excellent enantioselectivity (E >300) for the encapsulated lipase with an enantiomeric excess value of 98% for S-naproxen.     

Improvement of catalytic activity of lipase in the presence of wide rim substituted calix[4]arene carboxylic acid-grafted magnetic nanoparticles

Candida rugosa lipase immobilized on calix[4]arene carboxylic acid-grafted magnetic nanoparticles using a sol–gel encapsulation technique was tested for activity, which was assessed both in the enantioselective hydrolysis of racemic Naproxen methyl ester and that of p-nitrophenylpalmitate. It has also been noticed that, compared to the free enzyme (E = 137) with an ee value of >98 %, S-Naproxen calix[4]arene carboxylic acid-grafted magnetic nanoparticles based on encapsulated lipase (Calix-1-MN and Calix-2-MN) offer excellent enantioselectivity (E = 373 and E = 381). Moreover, the results indicated that after the fifth reuse in the enantioselective reaction, the encapsulated lipase (Calix-2-MN) still retained about 43 % of its conversion power.     

Calix[n]arene Carboxylic Acid Derivatives as Regulators of Enzymatic Reactions: Enhanced Enantioselectivity in Lipase-Catalyzed Hydrolysis of (R/S)-Naproxen Methyl Ester

Candida rugosa lipase was immobilized with a sol–gel encapsulation procedure in the presence and absence of a calix[n]arene carboxylic acid derivative grafted onto magnetic nanoparticles or in the presence of the calix[n]arene carboxylic acid derivative with Fe₃O₄ magnetic nanoparticles as an additive. Through the enantioselective hydrolysis of racemic naproxen methyl ester and the hydrolysis of p-nitrophenylpalmitate, the relative enzyme activity was evaluated and tested. These results show that the encapsulated lipase without supports has lower conversion and enantioselectivity compared to the Calix[n]COOH-based encapsulated lipase. It has also been observed that the Calix[4]COOH-based encapsulated lipase has excellent enantioselectivity (enantiomeric ratio (E)?>?400) as compared to encapsulated-free lipase enantioselectivity (E?=?137), and it also has an enantiomeric excess value of ~98 % for S-naproxen.     

水饱和离子液体中萘普生的酶法拆分

 考察了五种水饱和离子液体反应介质中固定化脂肪酶催化外消旋萘普生甲酯的水解. 结果表明,这些具有不同阴阳离子组合的咪唑基离子液体作为反应介质都能促进水解反应的有效进行,但在水饱和1-正丁基-3-甲基咪唑六氟磷酸盐(［bmim］PF6)中,反应进行得更快,转化率更高. 这些离子液体对脂肪酶均有一定的溶解作用并使溶解的脂肪酶失活. 脂肪酶在离子液体中的溶解度与其剩余活性之间有一定的相关性. 为了解决脂肪酶在离子液体中的溶解问题,使用非极性、高比表面积的无定形多孔硅胶YWG-C6H5对脂肪酶进行了固定化. 在水饱和［bmim］PF6中使用固定化脂肪酶催化反应,反应72 h的转化率为28.3%, 产物的对映体过量值为98.2%, 继续进行反应,转化率将增加,但产物的对映体过量值明显下降. 利用离子液体有别于传统有机溶剂的特性,对离子液体的循环使用、产物的回收和水的补充方法进行了研究. 在反复批式反应中,固定化脂肪酶连续使用五次,活性仅略微下降.     

Enzymatic resolution of 2-substituted tetrahydroquinolines. Convenient approaches to tricyclic quinoxalinediones as potent NMDA-glycine antagonists

Two approaches leading to the enantiomerically pure tricyclic quinoxalinedione class of NMDA-glycine antagonists using enzymatic resolutions are described. An intermediate, racemic methyl 1,2,3,4-tetrahydroquinoline-2-carboxylate 3, was resolved to (S)-3 in 97% ee and 47% yield (E=67) using -chymotrypsin. In an improved method, hydrolysis of another intermediate, racemic methyl 1,2,3,4-tetrahydroquinoline-2-acetate 4, with Novozym^® 435 provided the desired (S)-4 in high enantioselectivity and yield (93% ee, 50%, E=94).