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     

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。     

酶催化选择性酯化在蔗糖酯合成中的应用研究进展

较详细地综述了近年来国外酶催化选择性合成蔗糖酯方面的研究成果,对反应使用酶的类型、酶源、反应介质等对产物酰化位置以及取代数目的影响进行了分析,认为蔗糖酰化使用酶的类型主要有蛋白酶和脂肪酶,反应使用的介质除了普通有机溶剂、无溶剂反应外,还有离子液体和超临界流体;当用蛋白酶酰化时,反应大多优先发生在C-1′位置,部分优先在C-2位置,用脂肪酶酰化时,一般优先酰化C-6位置,然后是C-6′和C-1′位置。指出了在离子液体、超临界流体中蔗糖选择性酰化的反应是未来值得研究的重要内容。     

离子液介质中生物催化与生物转化的研究进展

Ionic liquids have negligibly low vapor pressure, high stability and polarity. They are regarded as green solvents. Enzymes, especially lipases, as well as whole-cell of microbe, are catalytically active in ionic liquids or aqueous-ionic liquid biphasic systems. Up to date, there have been many reports on enzyme-exhibited features and enzyme-mediated reactions in ionic liquids. In many cases, remarkable results with respect to yield, catalytic activity, stability and (enantio-, regio-) selectivity were obtained in ionic liquids in comparison with those observed in conventional media. Accordingly, ionic liquids provide new possibilities for the application of new type of solvent in biocatalytic reactions.     

n‐butane carbonylation to n‐pentanal using a cascade reaction of dehydrogenation and SILP‐catalyzed hydroformylation

A novel gas‐phase process has been developed that allows direct two‐step conversion of butane into pentanals with high activity and selectivity. The process consists of alkane dehydrogenation over a heterogeneous Cr/Al₂O₃ catalyst followed by direct gas‐phase hydroformylation using advanced supported ionic liquid phase (SILP) catalysis. The latter step uses rhodium complexes modified with the diphosphite ligands biphephos (BP) and benzopinacol to convert the butane/butene mixture from the dehydrogenation step efficiently into aldehydes. The use of the BP ligand results in improved yields of linear pentanal because SILP systems with this ligand are active for both isomerization and hydroformylation. © 2014 American Institute of Chemical Engineers AIChE J, 61: 893–897, 2015     

Enzymatic direct synthesis of acrylic acid esters of mono‐ and disaccharides

BACKGROUND: There is an increased need to replace materials derived from fossil sources by renewables. Sugar‐cane derived carbohydrates are very abundant in Brazil and are the cheapest sugars available in the market, with more than 400 million tons of sugarcane processed in the year 2007. The objective of this work was to study the preparation of sugar acrylates from free sugars and free acrylic acid, thus avoiding the previous preparation of protected sugar derivatives, such as glycosides, or activated acrylates, such as vinyl acrylate. RESULTS: Lipase catalyzed esterification of three mono‐ and two disaccharides with acrylic acid, in the presence or absence of molecular sieves was investigated. The reactions were monitored by high‐performance liquid chromatography (HPLC) and the products were analyzed by matrix‐assisted laser desorption ionization–time of flight (MALDI‐TOF) mass spectrometry. The main products are mono‐ and diacrylates, while higher esters are formed as minor products. The highest conversion to sugar acrylates was observed for the D ‐glucose and D ‐fructose, followed by D ‐xylose and D ‐maltose. Molecular sieves had no pronounced effect on the conversion CONCLUSIONS: A feasible method is described to produce and to characterize sugar acrylates, including those containing more than two acrylate groups. The process for production of these higher esters could potentially be optimized further to produce molecules for cross‐linking in acrylate polymerization and other applications. The direct enzymatic esterification of free carbohydrates with acrylic acid is unprecedented. Copyright © 2008 Society of Chemical Industry     

Rhodium‐catalyzed hydroformylation of unsaturated fatty esters in aqueous media assisted by activated carbon

Concerns about the environmental impact of chemical transformations prompted chemists to develop clean chemical processes using water as a solvent. Although appropriate for small partially water‐soluble molecules, these processes do not allow for the transformation of hydrophobic substrates due to the mass transfer limitation between the aqueous and the organic phase. In this context, we show that activated carbons can be used as mass transfer additives to promote the rhodium‐catalyzed hydroformylation of methyl oleate and other unsaturated olefins. Due to its mesoporous and hydrophobic character, the Nuchar®WV‐B activated carbon proved to be especially effective as mass transfer promoter. Actually, a significant increase in the conversion was observed. Additionally, more than 90% aldehydes were formed during the course of the reaction. When compared to other mass transfer promoters such as co‐solvents or cyclodextrins, Nuchar®WV‐B was by far the most efficient. Thus, the use of activated carbons appeared to be a suitable solution for the aqueous rhodium‐catalyzed hydroformylation of hydrophobic bio‐sourced substrates. Practical applications: The easiness with which the FAME hydroformylation could be implemented in water using activated carbons as mass transfer promoters is a major advantage in a context of an industrial–environmental approach. This finding is of importance as the obtained oxo‐products can be used in many industrial areas such as surfactants, polymers, or lubricants.     

Enzyme‐catalyzed copolymerization of oxiranes with dicarboxylic acid anhydrides

Ring‐opening copolymerizations of the oxiranes glycidyl phenyl ether (GPE) and diglycidyl ether of bisphenol A (DGEBA) with a dicarboxylic acid anhydride [methyl hexahydrophthalic anhydride, nadic anhydride, maleic anhydride (MA), or itaconic anhydride (IA)] were carried out with the lipases Candida cylindracea (CCL), Lipozyme TL‐IM (LIM), and Novozyme 435 (N435) as catalysts. The CCL‐catalyzed reaction of DGEBA with MA or IA (at a 1:2 molar ratio) at 80°C resulted in only partial curing. We monitored the reactions by Fourier transform infrared spectroscopy and by following the changes in the intensities of carbonyl stretching frequencies of the anhydride and ester groups. The reactivity of the oxirane group in GPE was higher than that in DGEBA; this may have been due to the higher viscosity of DGEBA. The reactivities of the enzymes for the copolymerization of the oxiranes and dicarboxylic acid anhydride were in the order LIM > CCL > N435. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 697–704, 2005     

Application of lipases to the regioselective synthesis of sucrose fatty acid monoesters

A regioselective synthesis of 6′-O-acyl sucrose monoesters has been developed through the lipase-catalyzed esterification of sucrose acetals with fatty acids in both organic solvents and under solvent-free conditions. The products were obtained in overall yields of 20–27% after hydrolysis of the isopropylidene groups with aqueous acids. The strict selectivity of the enzymes used also enabled the preparation of a monoester fraction that was highly enriched in 6-O-acyl sucrose. This was accomplished by lipase-catalyzed transesterification of sucrose monoesters, prepared by conventional chemical methods, in propan-2-ol. After removal of the transesterification products (sucrose and fatty acid isopropyl esters) and column chromatography on silica gel, the obtained monoester product contained 80% of the single regioisomer, 6-O-acyl sucrose.     

The synthesis of sucrose esters from telomer monocarboxylic acids

Glycolipid biosurfactants possess excellent surfactant properties and can be useful model compounds for the synthesis of surfactants from materials available in large quantities. The incorporation of a long, branched alkyl group, which is a feature of glycolipids, into a synthetic surfactant was achieved by the transesterification of sucrose with the methyl ester of a selected telomer monocarboxylic acid mixture, in a solution reaction. Characterisation showed the product to be a mixture of mono- and diesters each comprising a different ratio of linear to branched alkyl chains in the substituted group. Surfactant properties of the mixture, and the chromatographically-separated components, when evaluated in both distilled water and a salt solution, were found to be superior to a range of sucrose stearates. In addition the biosurfactant analogues were found to be more effective than surfactants derived from β-keto alkyl esters of various sugars (including sucrose) but were not as efficient as these latter compounds.     

Lipase‐catalyzed acylation of konjac glucomannan in ionic liquids

A comparative study was made of lipase‐catalyzed acylation of konjac glucomannan (KGM) with vinyl acetate as the acyl donor in five ionic liquids (ILs) and also in the presence of the organic solvent tert‐butanol (t‐BuOH). An obvious enhancement in enzyme activity and stability was observed using ILs as the reaction media when compared with t‐BuOH. The maximum degree of substitution (DS) of the modified KGM in ILs and t‐BuOH under the conditions employed is 0.71 and 0.54, respectively. The water activity (a_w) of the reaction system affected the acylation of KGM to some extent. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate (C₄MIm.BF₄) was the best IL medium for the reaction, and an a_w of 0.75 was optimum. It was also found that the nature of both the cation and the anion of ILs had an effect on the reaction. Candida antarctica lipase B immobilized on an acrylic resin (Novozym 435) displayed no acylation activity to KGM in 1‐butyl‐3‐methylimidazolium chloride (C₄MIm.Cl). The optimum reaction temperature for enzymatic acylation in ILs was shown to be 45‐55 °C. Enzymatic acylation of KGM in IL‐t‐BuOH co‐solvent systems was also investigated. When an appropriate amount of t‐BuOH was added to ILs, the DS of the modified KGM was enhanced. Additionally, the enzymatic acylation of KGM in all the media examined was shown to be regioselective, with acylation occurring predominantly at the C‐6‐OH. Copyright © 2006 Society of Chemical Industry     

Promoting the sulfuric acid catalyzed isobutane alkylation by quaternary ammonium ionic liquids

Seven typical quaternary ammonium ionic liquids, amino acid ionic liquids, and imidazolium ionic liquids were synthesized, characterized, and investigated as co-catalyst for the sulfuric acid catalyzed isobutane alkylation. The results show that the introduction of [OPSIm][HSO₄] or [Pr₃NPS][HSO₄] both leads to a better catalytic performance and higher quality of alkylate products. The molecular dynamic simulation indicates that the [OPSIm][HSO₄] can promote the dissolution of isobutane molecules at interface, further improving the ratio of isobutane to olefin from 1.02 to 1.18. Differently, the [Pr₃NPS][HSO₄] can significantly increase the interface width from 0.66 to 0.97 nm and reduce the interface tension from 28.49 to 14.62 mN/m, thereby enhancing the reaction area and improving the ion transfer. The [Pro][HSO₄] and [Gly][HSO₄] result in a worse quality of alkylate products due to no positive effect on the interfacial properties such as interfacial solubility of isobutane.     

Enzyme‐catalyzed synthesis of structured phospholipids with conjugated linoleic acid

Structured phospholipids were synthesized with the functional lipid conjugated linoleic acid (CLA). The lipase‐ and phospholipase A₂‐catalyzed enzymatic acidolysis reaction between phospholipids (PL) and CLA was used for fatty acid modification. Enzymatic processes were an effective way to produce structured PL. Screening of four lipases and immobilized phospholipase A₂ and a combination of lipase and phospholipase showed that only Lipozyme RM IM and Lipozyme TL IM were effective in incorporation of CLA into PL. The maximum incorporation achieved by the latter enzyme was 16% with soy PL in 72 h.     

离子液介质中生物催化与生物转化的研究进展

Ionic liquids have negligibly low vapor pressure, high stability and polarity. They are regarded as green solvents. Enzymes, especially lipases, as well as whole-cell of microbe, are catalytically active in ionic liquids or aqueous-ionic liquid biphasic systems. Up to date, there have been many reports on enzyme-exhibited features and enzyme-mediated reactions in ionic liquids. In many cases, remarkable results with respect to yield, catalytic activity, stability and (enantio-, regio-) selectivity were obtained in ionic liquids in comparison with those observed in conventional media. Accordingly, ionic liquids provide new possibilities for the application of new type of solvent in biocatalytic reactions.     

Improved Stability and Catalytic Activity of Palladium Nanoparticle Catalysts using Phosphine‐Functionalized Imidazolium Ionic Liquids

Palladium nanoparticles (Pd NPs) stabilized by 6 different phosphine‐functionalized ionic liquids (PFILs) were synthesized in imidazolium‐based ionic liquids (ILs) using H_2(g) (4 bar) as a reductant. Characterization showed well‐dispersed particles of ∼3 nm (TEM) and confirmed the PFIL stabilization of the NPs (XPS). The PFILs were composed of an imidazolium functionality separated from the phosphine group by a propyl or undecyl chain. The counter anions for both FILs and IL solvents were chosen from N‐bis(trifluoromethanesulfonyl)imide (Tf₂N⁻), trifluoromethanesulfonate (TfO⁻) or hexafluorophosphate (PF₆⁻). Colloidal suspensions of the Pd NPs were employed as biphasic hydrogenation catalysts for the reduction of the olefinic bond in styrene under mild conditions (50 °C, 4 bar H_2(g), 1.5 h). The PFIL‐stabilized Pd NPs were effective hydrogenation catalysts and showed superior activity and recyclability over NPs synthesized in the absence of PFILs. Poisoning tests of the Pd NP catalysts and characterization of the electronic properties of the phosphine were also performed.     

相转移催化合成玉米油蔗糖酯的研究

研究了以玉米油甲酯为原料代替单一脂肪酸合成玉米油蔗糖酯的工艺。考察了反应温度、催化剂种类和乳化利用量对实验结果的影响，确定了合成反应的较佳工艺条件。结果表明：在催化剂C用量约为玉米油甲酯质量的3％，乳化剂A用量为玉米油甲酯质量的8％，135℃下反应3．5h～4．5h时，玉米油甲酯转化率可达88．49％，其产品中油溶性蔗糖多酯质量分数可达67．9％；产品的表面张力为31．4mN／m，去污力为82．0％，脱脂力为36％，稳泡能力为10／8mm／mm(起始／5min)．HLB值为11．7。     

含羧酸基的功能化离子液体催化合成氯乙酸异丙酯

将合成的羧酸基功能化离子液体用于氯乙酸和异丙醇的酯化反应,考察了不同功能化离子液体的催化性能、不同的反应条件、反应结束后产物的分离和离子液体的循环使用。结果表明,以[C1imCH2COOH]HSO4为催化剂,n(氯乙酸)∶n(异丙醇)∶n(离子液体)=5∶5∶1,反应温度为60℃,反应时间为3 h的条件下,异丙醇的转化率为90.6%,氯乙酸异丙酯的选择性达到100%。反应结束后产物和离子液体分层明显,通过简单的倾倒就可以分离产物。分离后的催化剂重复使用5次,催化剂活性基本不变。     

离子液体催化合成酯研究进展

概述了不同种类离子液体在催化酯化反应中的应用。采用离子液体催化酯化反应,催化剂热稳定性好、效率高、环境友好且可回收重复利用,克服了传统方法普遍存在的副反应多、催化剂不易回收、设备腐蚀性大、环境污染以及后处理困难等缺点。探索了离子液体催化酯化的反应机理,指出了离子液体新体系发展需要解决的瓶颈问题及其在催化酯化反应中存在的不足,展望了离子液体在催化酯化反应中的发展方向。