重要文章导读

纳米色料的制备及应用；亚氨基二乙酸的生产与应用；微反应器技术在精细化工中的应用；高纯乙酰氯生产工艺的改进；甲基丙烯酸甲酯-丙烯酸共聚物磁性微球的制备及其应用；酶催化选择性脱酰作用在糖酯合成中的应用研究进展；有机硅耐高温涂料的研究；[编按]     

脂肪酶催化糖酯合成的研究进展

糖酯是应用广泛的无毒非离子表面活性剂。相比于传统化学合成方法,酶催化合成糖酯具有众多优点,非常适合于食品添加剂的生产。酶催化合成糖酯的研究主要集中在酶的筛选,反应介质,反应底物,反应条件等方面。本文主要对近年来酶催化合成糖酯研究进展进行论述,并讨论了其中的问题和发展方向。     

酶催化区域选择性合成蔗糖酯的研究进展

详细综述了非水相酶催化合成蔗糖酯的研究进展。主要介绍了酶的种类、反应介质、底物性质、外加辅助手段等因素对蔗糖酯产率以及对酶区域选择性的影响。酶催化区域选择性合成蔗糖酯的难点在于蔗糖具有多个可酰化羟基及其与酰基供体的不相溶性,提出通过介质工程、底物修饰改性、外加物理场如微波和超声波辅助等改善底物相溶性,通过筛选酶、蔗糖修饰等可以得到高区域选择性的蔗糖酯。最后指出酶催化合成蔗糖酯存在的问题、发展前景等。     

非水相中酶法合成糖酯的研究进展

回顾了非水相酶法合成糖酯的研究进展,重点介绍了葡萄糖酯、果糖酯、蔗糖酯、麦芽糖酯和木糖醇酯的合成方法,分析了酶、溶剂、脂肪酸等对糖酯收率的影响,比较了不同糖酯酶法合成的相似性及差异性。并对其研究方向和发展前景进行了展望:酶法合成糖酯具有反应条件温和、选择性高、低毒环保等优点;采用新型反应介质、寻求既经济又环保的分离纯化方法和降低成本是研究的重点。     

蔗糖酯的酶促合成研究进展

蔗糖酯是通过脂肪酸类化合物和蔗糖合成的一种重要食品添加剂。相对于化学催化,酶催化条件温和,操作简单,更具有高的选择性。就蔗糖酯不同位置上的选择性酶促合成进展做一综述.     

离子液体在酶促合成糖酯中的应用

糖酯是一类非离子型生物表面活性剂,广泛应用于食品、医药、化妆品行业,部分糖酯及其衍生物还具有抗肿瘤和抗菌活性。在糖酯传统合成方法中,存在着糖类易焦化、区域选择性差、有机溶剂残留、酶易失活等问题。离子液体作为环境友好溶剂和催化剂,具有结构可设计等优势,成为糖酯合成研究中热点领域,本文总结其优缺点,指出今后的研究重点。     

生物催化在糖苷合成中的应用

较详细地综述了目前国外生物催化合成糖苷的研究进展,并对生物催化制备糖苷的酶的种类、反应介质、反应机理、反应类型及其影响因素进行了介绍。比较了各种生物催化合成糖苷的方法:糖苷酶催化合成糖苷产率一般较低;糖基转移酶需要以昂贵的活化的核苷糖作为糖基供体在辅酶的参与下合成糖苷;用糖苷合成酶合成寡糖,不仅具有立体选择性和区域选择性,而且效率高、底物便宜;全细胞催化合成糖苷具有产率较高,环境友好,产物纯度高且易分离等优点。认为全细胞催化是糖苷合成的重要方法,具有重要的应用价值,该方法值得深入研究。     

阿糖胞苷衍生物的可控选择性酶促合成与表征

应用简单有效的酶促合成方法可控选择性地合成阿糖胞苷不同官能团的酰化衍生物。通过酶与溶剂之间的选择性调控实现了己二酸二乙烯酯对阿糖胞苷糖环上5′-OH和嘧啶环上4-N的可控选择性酰化,采用FTIR和NMR分析手段对所得到的衍生物的结构进行了确定,并考察了底物摩尔比,反应时间,反应温度对产率的影响。结果表明:脂肪酶Novozym435在无水丙酮中对C′-5位的伯羟基上显示较高的化学选择性,得到单一的5′-O-乙烯己二酰-阿糖胞苷衍生物,产率达到69%,而脂肪酶PS‘Amano’(PS)在无水吡啶中选择性地在N-4位的伯氨基上发生酰化,得到单一的4-N-乙烯己二酰-阿糖胞苷衍生物,产率达到58%。     

抗抑郁药帕罗西汀的合成研究进展

介绍了抗抑郁药帕罗西汀及其中间体的合成概况,重点评述了酶催化去对称化法的新进展及近年报道的手性催化共轭加成、手性催化还原、手性催化还原环合等几种新方法,建议重点开发内消旋1-甲基-4-对氟苯基-2,6-二氧代哌啶-3,5-二羧酸酯经酶催化对映选择性水解、脱羧制备（3S,4R）-1-取代-4-对氟苯基-2,6-二氧代哌啶-3-羧酸酯的方法,认为酶催化去对称化法和手性催化法为今后发展的重点。     

有机相酶法合成己二酸单乙烯蔗糖酯的研究

以蔗糖和己二酸二乙烯酯(DVA)为原料,采用单因素法和均匀设计法对脂肪酶Novozym-435在有机溶剂中选择性地催化合成己二酸单乙烯蔗糖酯进行了研究。考察了有机溶剂种类及含水量、反应温度、酶质量浓度、底物摩尔比对产物产率的影响,得到蔗糖单(己二酸单乙烯酯)酯(SMVA)、蔗糖双(己二酸单乙烯酯)酯(SDVA)的适宜合成条件及相应的产率分别为:在叔丁醇介质中,不含水,反应温度49℃,酶质量浓度30 mg/mL,糖酯摩尔比1∶3.2的条件下,反应4 d,SMVA的产率为13.69%;在丙酮介质中,不含水,反应温度47.5℃,酶质量浓度30 mg/mL,糖酯摩尔比1∶3.3的条件下,反应3 d SDVA的产率为28.82%。用FTIR、HPLC、HPLC-MS和TLC等对产物SMVA、SDVA等进行了表征。     

Enzyme‐catalyzed regioselective synthesis of sugar esters and related compounds

In this review, a comprehensive and illustrative survey is made of the regioselective synthesis of esters of sugars and related compounds using lipases. The main emphasis has been given to the screening and use of commercially available lipases for the enzymatic esterification of neutral monosaccharides, disaccharides, sugar alcohols and their selected ether and ester derivatives. The effect of solvents and solubilizing agents in improving the yields of the resultant sugar fatty acid esters has been incorporated. Further, solvent‐free esterification with molten fatty acids, use of ionic liquids and microwave radiations for improvement in the methodology have also been discussed. Copyright © 2006 Society of Chemical Industry     

Amino Alcohols in Organocatalysed Acylation and Deacylation: The Effect of Dialkylamino Substituents on the Rate

In alcohols and esters, a neighbouring dialkylamino group can enhance the reactivity towards acylation and deacylation, respectively, that is, such amino alcohols can act as transacylation catalysts like DMAP. This effect is dependent on the number of (carbon) spacer atoms, flexibility of the molecule and the presence and position of further heteroatoms. Based on this effect, the site selective acylation and deacylation of desmycosin, a macrocycle antibiotic possessing an amino sugar moiety, is described.     

二丁基氧化锡在糖衍生物选择性合成中的应用

二丁基氧化锡和糖上的羟基选择性地形成亚甲锡烷基缩醛,通过聚合作用使处于聚合体不同位置的羟基显示了不同的电负性和亲核性,进行选择性反应合成糖衍生物.因此,利用二丁基氧化锡这种反应特性,分别对其在活性糖的保护、形成糖聚合体和糖基化等方面的应用进行了阐述,为该试剂在糖衍生物合成中的广泛应用提供参考.     

Branched aliphatic polyesters by ring-opening (co)polymerization

The rapid development of biodegradable and biocompatible materials for biomedical applications is reflected in the search for new methods for aliphatic polyester modification applicable in this field. One possible approach is modification by changes to the polymer topology.This review covers the main methods of synthesis of branched aliphatic biodegradable and biocompatible (co)polyesters, where the ring-opening polymerization (ROP) of cyclic esters or cyclic carbonates is the leading process. First, literature examples of ring-opening multibranching polymerization (ROMBP) of AB₂-type hydroxyl-substituted cyclic lactones, lactides and carbonates are cited followed by the presentation of the application of AB-type cyclic esters and additionally AB₂ cyclic ethers or esters as “branching monomers” for the synthesis of branched polyesters based on polycaprolactone (PCL), polylactide (PLA) and polyglycolide (PGA). In the following part, methods involving the combination of the ROP of AB-type cyclic esters and condensation processes leading to branched structures are summarized. Other related strategies leading to “dendri-star” or “core–shell” copolyesters are also discussed. Several examples of approaches to PCL and PLA graft copolymer syntheses are also shown. The advantages and disadvantages of the presented methodologies of branched polyester synthesis are highlighted. Finally, the influence of the branched structure on the properties of the presented class of polyesters, important from the application point of view, is considered.     

Regioselective one-pot protection and protection-glycosylation of carbohydrates

Deciphering the roles and structure-activity relationships of carbohydrates in biological processes requires access to sugar molecules of confirmed structure and high purity. Chemical synthesis is one of the best ways to obtain such access. However, the synthesis of carbohydrates has long been impeded by two major challenges--the regioselective protection of the polyol moiety of each monosaccharide building block and the stereoselective glycosylation to produce oligosaccharides of desired length. Here, we review the development of the first regioselective protection-glycosylation and a revolutionary regioselective combinatorial one-pot protection of monosaccharides that can be used to differentiate the various hydroxy groups of monosaccharides with a vast array of orthogonal protective groups in one-pot procedures.     

Linear carboxylic acid esters from α-olefins: 3. Catalysis by dispersions of palladium complexes

Linear, fatty-type, carboxylic acid esters are prepared by regioselective 1-alkene carbonylation catalyzed by dispersions of ligand-stabilized palladium(II) chlorides in quaternary Group VB salts of trichlorostannate(II). The sensitivity of these syntheses to catalyst composition and alkene structure is described, together with techniques for multiple cycling and regeneration of the preferred palladium formulation, PdCl₂[P(C₆H₅)₃]₂-10[(C₂H₅)₄N][SnCl₃]. For parts 1 and 2 in this series, see References 1 and 2.     

Chemo-enzymatic synthesis of disaccharide fatty acid esters

A novel enzymatic method for the synthesis of disaccharide fatty acid esters was developed with immobilizedMucor miehei lipase (Lipozyme IM-60; Novo Nordisk, Bagsvaerd, Denmark) as a catalyst. A range of lactose and maltose monoesters was prepared in overall yields of 48–77% from the corresponding sugar acetals and fatty acids.     

Enzyme‐catalyzed regioselective synthesis of sucrose‐based esters

Sucrose‐based esters are nonionic biosurfactants, which can be synthesized from the enzyme‐catalyzed esterification/transesterification of sucrose. The multi‐hydroxyl groups of sucrose and the immiscibility of sucrose with the acyl donors are the main bottlenecks in obtaining highly regioselective sucrose‐based esters. In this mini‐review, the effects of reaction conditions such as biocatalysts, design of solvent systems used as reaction media, modification and denaturation of substrates, and coupling with external auxiliary physical fields such as microwave irradiation and ultrasonic waves on the yield of sucrose esters and regioselectivity of products are highlighted. The existing problems in the field of enzymatic synthesis of sucrose esters as well as its future perspectives were pointed out. Copyright © 2011 Society of Chemical Industry     

Separation of tocopherol homologues by selective deacylation and chromatography

Isolation of tocopherol homologues can be accomplished by selective deacylation of tocopheryl esters followed by chromatographic separation of the esters from the free tocopherols.     

Membranes in the enzymatic synthesis of biotensides from renewable sources

A novel integrated process of enzymatic synthesis of sugar fatty acid esters from renewable sources was proposed for the system oleic acid/-methylglucoside focussing on the application of different membrane techniques. The operational parameters were studied and optimised carrying out the reaction in an enzymatic membrane reactor (EMR) where the catalyst remained retained by means of ultrafiltration. A pervaporation unit coupled to the EMR was applied for by-product removal (water). A proper product separation and isolation was achieved applying combined techniques including filtration, evaporation, extraction and alternatively stepwise elution chromatography or dialysis.