L-抗坏血酸硬脂酸酯的合成条件探索

文章对L-抗坏血酸硬脂酸酯的最佳合成条件进行探索。通过各种不同的实验条件得出最佳合成条件为：抗坏血酸比硬脂酸甲醣为1：1．3（摩尔比）,催化剂浓硫酸比（抗坏血酸＋硬脂酸甲酪）为1：0．10（摩尔比）,反应温度24℃,反应时闯24h。在此条件下可获得总产率为77％的抗坏血酸硬脂酸酯。考察了以硬脂酸甲酯和L-抗坏血酸为原料,通过酯交换法合成L-抗坏血酸硬脂酸酯的最佳合成条件。文章对L-抗坏血酸硬脂酸酯的最佳合成条件进行探索。通过各种不同的实验条件得出最佳合成条件为：抗坏血酸比硬脂酸甲酯为1：1.3（摩尔比）,催化剂浓硫酸比（抗坏血酸＋硬脂酸甲酯）为1：0．10（摩尔比）,反应温度24℃,反应时间24h。在此条件下可获得总产率为77％的抗坏血酸硬脂酸酯。考察了以硬脂酸甲酯和L-抗坏血酸为原料,通过酯交换法合成L-抗坏血酸硬脂酸酯的最佳合成条件。     

薄层层析法分析醋酸麦迪霉素合成中间体

用薄层层析法来定性分析醋酸麦迪霉素合成过程的酰化中间体。通过对多种有机溶剂体系的试验，发现由脂肪醇、脂肪酸酯和芳烃组成的三元体系和碱性硅胶Ｇ板可获得满意的效果。     

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。     

L-抗坏血酸-2-硫酸酯盐的合成

以焦硫酸钾为酯化剂，以吡啶为溶剂合成了Ｌ－ 抗坏血酸的稳定衍生物 Ｌ－ 抗坏血酸－ ２ － 硫酸酯二钾盐。该衍生物具有弱酸性，在弱碱中稳定。合成方法操作简便，收率高。     

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     

Enzymatic Formation and Physico-Chemical Behaviour of Uncommon Monoglycerides

Results on the enzymatic monoacylation of glycerol by aid of phenylboronic acid in organic solvents are presented. The comparison of two alternative methods indicates that the ?2-step-method”? (synthesis in one batch unit without isolation of intermediates) is in total more favourable than the ?3-step-method”? (synthesis in two batch units including isolation of intermediates), although yields are somewhat lower. Probably this disadvantage originates from an enzyme inhibition caused by residual free phenylboronic acid in the reaction system. Several varying uncommon fatty acids like (S)-17-hydroxyoctadecanoic acid, 12-hydroxyoctadecanoic acid and 2-hydroxyhexadecanoic acid have been used as oleo-components. As far as no steric hindrance is caused by these substrates, product formation is about 80% (basis ?2-step-method”?). Investigations at the Langmuir film balance showed different film states with specific transition phases for the 1(3)-(17-hydroxy)-octadecanoyl and the 1(3)-(12-hydroxy)-octadecanoyl glycerol. The monoglyceride of the 2-hydroxyhexadecanoic acid proved to be a good emulsifier. Its qualities in this respect were confirmed by the data of the surface and interfacial tension versus n-hexadecane and also by the outcome of the emulsification tests. The enzymatic acylation of a diol like 1,3-propanediol led to the 1-(17-hydroxy)-octadecanoyl-3-propanol (yield: 50%). The film behaviour of this ester was similar to that of the corresponding monoglyceride.     

Lipase made active in hydrophobic media

Enzymes are distinguished from other catalysts by their high substrate specificity. This is a great asset when one wants to apply them for syntheses of various compounds. Their usage, however, generally is limited to hydrophilic reaction media, because they usually are not soluble and active in hydrophobic media. Recently, we have been able to make various enzymes soluble and active in highly hydrophobic organic solvents. The key to this success is the chemical modification of enzymes with an amphipathic synthetic polymer, polyethylene glycol. The activated polymers can be attached to enzymes in aqueous buffer solutions, and once enzymes are modified they become soluble and active in various organic solvents such as benzene, toluene and cholorinated hydrocarbons and exhibit high enzymic activities in these organic solvents. Modified hydrolytic enzymes catalyzed the reverse reaction of hydrolysis in organic solvents. The modified lipase catalyzed various ester synthesis reactions. Because the reactions were conducted in the pure solvent system, it also was possible to study the kinetics and the substrate specificity for ester synthesis reaction. It also catalyzed the polymerization of a hydroxy group containing carboxylic acid due to the bifunctional nature. The modified lipase catalyzed ester exchange between an ester and an alcohol, between an ester and a carboxylic acid and between two esters in organic solvents. When the two substrates for ester exchange were liquid, the reaction could take place without organic solvents. The modified lipase catalyzed an ester exchange reaction between trilaurin and triolein when dissolved in these substrates. Dilauroyl-monooleoylglycerol and monolauroyl-dioleoyl-glycerol were formed from these two substrates in the presence of the modified lipase. The modified enzyme was extremely thermostable in its substrates. In the ester synthesis and ester exchange reactions, a trace amount of water was necessary for expression of the enzymic activity. It is suggested that the amphipathic polymer molecules retained water in close proximity to the enzyme. Presented at the symposium “The Biology, Biochemistry and Technology of Lipase” at the 78th annual meeting of the American Oil Chemists’ Society held May 17–21, 1987, in New Orleans, Louisiana.     

Sugar ester-modified lipase for the esterification of fatty acids and long-chain alcohols

The esterification reaction of a long-chain fatty acid and a fatty alcohol with a surfactant-modified lipase in a microaqueousn-hexane system was studied. Various lipases from different sources were first modified with a surfactant of the sugar ester type to improve their dispersibility in apolar organic solvents. This enzyme modification technique converted inactive crude lipases to highly active biocatalysts for the esterification of long-chain fatty acids and fatty alcohols in a microaqueous n-hexane system. The hydrophilic-lipophilic balance value and chainlength of the fatty acid residue of the fatty acid sugar ester, used for modifying the lipases, significantly influenced the amount of precipitated lipase that was dissolved in the aqueous solution, the protein content of the lipase-surfactant complex and its esterification activity.     

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.     

Rapid synthesis of fatty acid esters for use as potential food flavors

Lipase-catalyzed esterification has been performed in hexane to generate novel mixtures of fatty acid esters from specially chosen combinations of fatty acids and alcohols. By varying the alcohol and enzyme compositions in the enzymatic reactions, different ester mixtures were produced, which were further purified and analyzed for ester composition by gas chromatography-mass spectrometry. Depending on the combination of alcohols and enzymes used, the final ester mixture exhibited significant compositional variation. These mixtures could be manipulated at the synthesis step, thereby enabling a high degree of product control. Such manipulation over enzyme-catalyzed ester synthesis in mixtures may be useful in the preparation of ester flavors for use in the food industry.     

Rapid synthesis of fatty acid esters for use as potential food flavors

Lipase-catalyzed esterification has been performed in hexane to generate novel mixtures of fatty acid esters from specially chosen combinations of fatty acids and alcohols. By varying the alcohol and enzyme compositions in the enzymatic reactions, different ester mixtures were produced, which were further purified and analyzed for ester composition by gas chromatography-mass spectrometry. Depending on the combination of alcohols and enzymes used, the final ester mixture exhibited significant compositional variation. These mixtures could be manipulated at the synthesis step, thereby enabling a high degree of product control. Such manipulation over enzyme-catalyzed ester synthesis in mixtures may be useful in the preparation of ester flavors for use in the food industry.     

Enzymatic Synthesis and Molecular Modelling Studies of Rhamnose Esters Using Lipase from Pseudomonas stutzeri

Rhamnolipids are becoming an important class of glycolipid biosurfactants. Herein, we describe for the first time the enzymatic synthesis of rhamnose fatty acid esters by the transesterification of rhamnose with fatty acid vinyl esters, using lipase from Pseudomonas stutzeri as a biocatalyst. The use of this lipase allows excellent catalytic activity in the synthesis of 4-O-acylrhamnose (99% conversion and full regioselectivity) after 3 h of reaction using tetrahydrofuran (THF) as the reaction media and an excess of vinyl laurate as the acyl donor. The role of reaction conditions, such as temperature, the substrates molar ratio, organic reaction medium and acyl donor chain-length, was studied. Optimum conditions were found using 35 °C, a molar ratio of 1:3 (rhamnose:acyldonor), solvents with a low logP value, and fatty acids with chain lengths from C4 to C18 as acyl donors. In hydrophilic solvents such as THF and acetone, conversions of up to 99–92% were achieved after 3 h of reaction. In a more sustainable solvent such as 2-methyl-THF (2-MeTHF), high conversions were also obtained (86%). Short and medium chain acyl donors (C4–C10) allowed maximum conversions after 3 h, and long chain acyl donors (C12–C18) required longer reactions (5 h) to get 99% conversions. Furthermore, scaled up reactions are feasible without losing catalytic action and regioselectivity. In order to explain enzyme regioselectivity and its ability to accommodate ester chains of different lengths, homology modelling, docking studies and molecular dynamic simulations were performed to explain the behaviour observed.     

Enzymatic removal of 3‐monochloro‐1,2‐propanediol (3‐MCPD) and its esters from oils

3‐Monochloro‐1,2‐propanediol (3‐MCPD) is a contaminant in processed food well known for about 30 years. More recently, this compound has observed attendance due to its occurrence as fatty acid esters in edible oils and products derived from them. In this study, the first enzymatic approach to remove 3‐MCPD and its esters from aqueous and biphasic systems by converting it into glycerol is described. First, 3‐MCPD was converted in an aqueous system by an enzyme cascade consisting of a halohydrin dehalogenase from Arthrobacter sp. AD2 and an epoxide hydrolase from Agrobacterium radiobacter AD1 with complete conversion to glycerol. Next, it could also be shown, that the corresponding oleic acid monoester of 3‐monochloropropanediol‐1‐monooleic‐ester (3‐MCPD‐ester) was converted in a biphasic system in the presence of an edible oil by Candida antarctica lipase A to yield free 3‐MCPD and the corresponding fatty acid. Hence, also 3‐MCPD‐esters can be converted by an enzyme cascade into the harmless product glycerol. Practical applications: Since several reports have been recently published on the contamination of foods with 3‐MCPD and its fatty acid esters, there is a great demand to remove these compounds and an urgency to find useful methods for this. In this contribution, we present an easy enzymatic way to remove 3‐MCPD and its esters from the reaction media (i.e., plant oil) by converting it to the nontoxic glycerol. The method requires neither high temperature nor organic solvents.     

Lipase made active in hydrophobic media by coupling with polyethylene glycol

Lipases from various microorganisms were chemically modified with polyethylene glycol derivatives: 2,4-bis[O-methoxypoly(ethylene glycol)]-6-chloro-s-triazine (activated PEG₂, a chain-shaped polymer) and copolymer of polyoxyethylene allyl methyl diether and maleic anhydride (activated PM, a comb-shaped polymer). Because each polymer is amphipathic, the modified lipases become soluble not only in aqueous solution but also in hydrophobic media. They exhibit potent catalytic actions for ester synthesis and ester exchange reactions, the reverse reaction of hydrolysis, in transparent organic solvents and also in oily substrates without organic solvents. With PEG₂-lipases, macrocyclic lactone and gefarnate (geranyl farnesylacetate) were synthesized in high yields from 16-hydroxy-hexadecanoic acid ethyl ester and from farnesylacetic acid and geraniol in organic solvents, respectively. The modified lipase catalyzed the esterification preferentially with the (R)-isomer of secondary alcohols. Because the ester synthesis reactions with modified lipase proceeded in the transparent benzene system, the kinetic parameters (Michaelis constant and maximum velocity) were obtained by reciprocal plotting according to the Michaelis equation. With comb-shaped polymer as modifier, PM-lipase catalyzed effectively the reverse reaction of hydrolysis in organic solvents. The properties of each modified lipase are discussed in relation to those of the nonmodified lipase. Presented at the 84th Annual Meeting of the American Oil Chemists' Society held on April 25–29, 1993, in Anaheim, CA.     

Lipase-Catalyzed Solid Phase Synthesis of Sugar Esters

Lipase-catalyzed synthesis of sugar fatty acid esters was performed in a heterogeneous reaction system in the presence of an organic solvent serving as adjuvant. Although the sugar is almost insoluble in such a system, high conversions to the corresponding sugar esters were achieved, due to crystallization of the product. Acylation occurred regioselectively at the primary hydroxyl group and subsequent diacylation was observed only in the case of caprylic acid (2–5%). Best conditions were found for solvents having low log P values and low product solubility such as acetone, using immobilized lipase from Candida antarctica (CAL-B, Novo SP435) and fatty acids with chain lengths from C₁₂ to C₈ as acyl donors. The esterification of β-D(+)-glucose with stearic acid resulted in up to 100% conversion after 48 hours equal to a productivity of 0.4 mmol sugar ester per gram lipase and hour.     

A GREENER SYNTHESIS TECHNOLOGY FOR LOMEFLOXACIN HYDROCHLORIDE

Lomefloxacin ethyl ester was prepared from 2,3,4-trifluoroaniline in ionic liquid in a one-pot procedure by condensation with EMME (ethoxymethylenemalonic diethyl ester), cyclization, ethylation, and condensation with 2-methyl piperazine. After its hydrolysis and salifying with hydrochloric acid, lomefloxacin hydrochloride was obtained with an overall yield of 58.4%. Compared with current lomefloxacin hydrochloride synthesis technology, this approach simplified its synthesis procedures, shortened its synthesis time, and eliminated the usage of volatile organic solvents.     

PVC塑料用环氧脂肪酸甲酯增塑剂的研制

介绍了聚氯乙烯（PVC）增塑剂环氧脂肪酸甲酯的制备方法：采用生物型脂肪酸甲酯为原料,双氧水为给氧体,有机酸作载体,在不使用任何溶剂、稳定剂和酸性催化剂的条件下,采用封闭式冷却循环装置一步法制得环氧增塑剂产品;讨论丁环氧脂肪酸甲酯在PVC生产中的应用情况。     

Chemo‐enzymatic synthesis of lipophilic ferulates and their evaluation for antioxidant and antimicrobial activities

An efficient chemo‐enzymatic synthesis of ferulic acid‐based structured lipids mimicking triacylglycerol with a pendant phenolic moiety was carried out for the first time. Initially, ferulic acid was reduced to coniferyl alcohol, followed by its esterification with fatty acids. The key step in the synthesis was dihydroxylation of the olefinic side chain of coniferyl ester, which was eventually esterified with fatty acids to generate phenolic structured lipids. Two such compounds of varying fatty acid chain lengths were synthesized in good yield. Structural confirmation of both compounds is based on IR, ¹H and ¹³C NMR, and MS techniques. The synthesized compounds were tested for in vitro antioxidant and antimicrobial activities. Both compounds exhibited moderate to good antioxidant activity. The phenolic structured lipid with only shorter‐chain fatty acids showed antibacterial activity. Both compounds did not show any antifungal activity.     

生物表面活性剂催化合成蔗糖酯及其应用

蔗糖酯是一种有效的食品添加剂,它可由蔗糖与脂肪酸酯或甘油酯在碱性催化条件下由有机溶剂法或无溶剂法合成得到,报道了蔗糖酯的合成,分离和应用进展,还论述了生物表面活性剂作为均相催化剂在蔗糖酯合成中的作用。     

Synthesis of mixed-acid phosphatidylcholines and high pressure liquid chromatographic analysis of isomeric lysophosphatidylcholines

A new method for the synthesis of mixed-chain phosphatidylcholines is reported. Silver ion catalyzed acylation of lysophosphatidylcholines by 2-thiopyridyl esters occurs rapidly (10 min) at room temperature in organic solvents. Yields of isomerically pure mixed-chain phosphatidylcholines (>98% isomeric purity) are generally greater than 80%. The reaction proceeds with only 1.5- to 2-fold excess of thiopyridyl ester, thus offering some advantages over existing procedures when precious acylating agents are used. The major disadvantage of the procedure is its sensitivity to water. Phosphatidylcholines having hydroxy fatty acyl groups are prepared by protection of the hydroxyl as the levulinate ester, conversion to the 2-thiopyridyl ester, acylation, and removal of the levulinate with hydrazine. For purification of lysophosphatidylcholines, a reverse-phase high pressure liquid chromatographic method for separation of 1-acylglycerophosphocholines from 2-acylglycerophosphocholines was developed.