交联酶聚集体与仿生硅化技术结合制备固定化脂肪酶

将交联酶聚集体(CLEAs)与仿生硅化技术相结合,制备了交联脂肪酶Candidasp.99-125杂化生物催化剂.以京尼平为交联剂,在最佳条件下制得的脂肪酶CLEAs的酶活达771U/g,回收率达75%;保护剂聚乙烯亚胺(PEI)与Candidasp.99-125脂肪酶共沉淀制备P/CLEAs,其酶活达897U/g,回收率约88%;利用PEI的诱导作用,在P/CLEAs表面形成氧化硅涂层,制得的脂肪酶CLEAs(Coated-CLEAs)显示出良好的稳定性,特别是其抗蛋白酶水解能力、有机溶剂耐受能力、重复使用性能等方面明显提高.     

Preparative regioselective acylation of glycols by enzymatic transesterification in organic solvents

Porcine pancreatic lipase can catalyze transesterification reac tions in organic solvents in a highly regioselective manner. Lipase powder was suspended in solutions of various diols in ethyl carboxylates, and the mixtures were shaken at 30°C; as a result, pri mary monoesters of glycols were produced on a preparative scale.     

Regioselective acylation of nucleosides and their analogs catalyzed by Pseudomonas cepacia lipase: enzyme substrate recognition

The substrate recognition of Pseudomonas cepacia lipase in the acylation of nucleosides was investigated by means of rational substrate engineering for the first time. P. cepacia lipase displayed excellent 3′-regioselectivities (96 to >99%) in the lauroylation of 2′-deoxynucleosides 1a-1e, while low to good 3′-regioselectivities (59-89%) in the lauroylation of ribonucleosides 1f-1j. It might be due to the unfavorable hydrogen bond interaction between 2′-hydroxyl group of 1f-1j and phenolic hydroxyl group of tyrosine residue present in the alternate hydrophobic pocket of the enzyme, which stabilizes the conformation of 5′-acylation transition state and thus increases the amount of the minor regioisomer. In addition, various ester derivatives of floxuridine were synthesized successfully by the lipase with high conversions (99%) and good to excellent 3′-regioselectivities under mild conditions. The recognition of various acyl donors by the enzyme was examined. The enzymatic recognition of acyl groups was rationalized in terms of the structure of the active site of the lipase, especially the size, shape, and physicochemical properties.     

微波辐射催化合成肉桂酸苄酯

肉桂酸苄酯是一种具有弱苏合香、花香等香气的香料,主要用于配制龙蜒香,在东方型香脂中作为定香剂,也可用作皂用、化妆用及果实香精的调香配料。肉桂酸苄酯的合成,在工业上,主要采用肉桂酸钠与氯化苄在二乙胺作用下反应,反应时间长达17h,产率80％以上。近年来的研究     

微波辐射下咪唑类离子液体催化安息香缩合反应研究

探讨了微波辐射下四种咪唑类离子液体催化不同取代基芳香醛的安息香缩合反应,并对反应条件进行了优化。结果表明,[Bmim]Im是合成目标产物的良好催化剂,在微波辐射时间5min、反应温度55℃、催化剂用量x([Bmim]Im)=1%、溶剂THF15m L、芳香醛用量5mmol、50%氢氧化钠水溶液0.5m L时,最高产率可达到81%。该方法耗时短、环境友好。在考查的底物中,除高位阻和具有较强p-π共轭效应的2-氯苯甲醛和4-甲氧基苯甲醛没有检测到产物外,其他不同取代芳香醛均得到了相应产物。反应后离子液体可以回收循环使用至少4次。     

Kinetic resolution of cyanohydrins via enantioselective acylation catalyzed by lipase PS-30

By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic cyanohydrins has been achieved via enantioselective acylation. The values of kinetic enantiomeric ratio (E) reached up to 314. Substituent effect is also briefly discussed.     

Kinetic resolution of mandelate esters via stereoselective acylation catalyzed by lipase PS-30

By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic mandelate esters has been achieved via stereoselective acylation. The value of kinetic enantiomeric ratio (E) reached up to 197.5. Substituent effect is briefly discussed.     

Enzyme-catalyzed direct three-component aza-Diels–Alder reaction using lipase from Candida sp.99–125

The direct three-component aza-Diels–Alder reaction was conducted with lipase as a catalyst for the first time. Under the optimized conditions, the aza-Diels–Alder reaction catalyzed by lipase from Candida sp.99–125 provided the products in moderate to excellent yields. Meanwhile, the endo/exo ratio reached up to 88:12.     

Kinetic resolution of allylic alcohols via stereoselective acylation catalyzed by lipase PS-30

By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic allylic alcohols has been achieved via stereoselective acylation. The value of kinetic enantiomeric ratio (E) reached up to 968. Substituent effect is briefly discussed.     

Kinetic modeling of vinyl acetate telomerization catalyzed by metal transition complexes under thermal and microwave heating

A kinetic model for the redox-initiated radical telomerization of vinyl acetate activated by microwave irradiation is presented. Four approaches based on the “microwave” or “thermal” effects were used to study the cases under microwave irradiation. One of the models assumes microwave-induced generation of radicals from monomer. The second model considers higher reaction temperatures than those reported in the experiments. The third model assumes that microwave radiation affects specifically catalyst-involved reactions. The fourth model is a combination of the second and third ones. The kinetic model captures well the effect of initiator, catalyst and solvent contents, as well as absence or presence of microwave irradiation, on polymerization rate and molecular weight development. Limiting monomer conversions and fairly constant values of number average molecular weight and molar mass dispersity were predicted by the model, which agrees with experimental observations.     

Highly chemoselective lipase from Candida sp. 99-125 catalyzed ring-opening polymerization for direct synthesis of thiol-terminated poly(ε-caprolactone)

Lipase from Candida sp. 99-125 catalyzed ring-opening polymerization of ε-caprolactone in the presence of 6-mercapto-1-hexanol was presented as a new metal-free approach for direct synthesis of welldefined thiol-terminated poly(ε-caprolactone). Remarkably, high chemoselectivity of lipase from Candida sp. 99-125 toward hydroxyl and thiol was exhibited and quantitative thiol fidelity over 90% was achieved. The tedious protecting/deprotecting steps for thiol and metal residue were avoided. The polymerizations with around 70% monomer conversion were conducted in bulk and toluene at relative low temperature of 40 ℃. Number-average molecular weight of resulted polymers ranged from 3000 to 4700 Da by changing the feed ratio between monomer and initiator. The structures of obtained thiolterminated poly(ε-caprolactone) were demonstrated by combining NMR and SEC analyses.     

Meglumine sulfate catalyzed solvent-free one-pot synthesis of coumarins under microwave and thermal conditions

A convenient method has been developed for the Pechmann reaction of phenols and β-keto esters catalyzed by meglumine sulfate. Solvent-free conditions, inexpensive catalyst, short reaction times, high yield, and ease of purification of the products are the advantages of this protocol. This novel catalytic system is expected to contribute to the development of more benign Pechmann condensation reactions of phenols with β-keto esters.     

Atom-efficient coupling reaction of aryl bromides with sodium tetraphenylborate catalyzed by reusable Pd/C in water under focused microwave irradiation

A rapid and heterogeneous Pal/C-catalyzed atom-efficient phenylation of aryl bromides by sodium tetraphenylborate takes place under focused microwave irradiation in water.The palladium catalyst can be easily recovered and reused.     

Highly regioselective propanoylation of dihydroxybenzenes mediated by Candida antarctica lipase B in organic solvents

Candida antarctica lipase B (CAL-B) was found to be a highly active biocatalyst for the direct acylation of the phenolic hydroxyls of substituted hydroquinones and resorcinols with vinyl propanoate as an acyl donor. The acylation reactions took place generally in a very regioselective manner. Especially in the case of 4-substituted resorcinols, the hydroxyl remote from the substituent was regiospecifically acylated to afford only the 1-O-propanoylated resorcinols.     

Study of CuI catalyzed coupling reactions of aryl bromides with imidazole and aliphatic amines under microwave dielectric heating

Amination of a variety of functionalized aryl bromides with imidazole and primary and secondary amines was accomplished using a CuI/amino acid catalyst system under microwave heating. Application of microwave irradiation shortened the reaction time from 25–40 h to 6–20 min. Good to very good yields of the corresponding coupling products were obtained when imidazole and secondary amines were used as starting materials. In case of primary amines, the outcome of the reaction was dependent on the character of the substituent on aryl bromide.     

Production of biodiesel by immobilized Candida sp. lipase at high water content

A new process for enzymatic synthesis of biodiesel at high water content (10–20%) with 96% conversion by lipase from Candida sp. 99–125 was studied. The lipase, a no-position-specific lipase, was immobilized by a cheap cotton membrane and the membrane-immobilized lipase could be used at least six times with high conversion. The immobilized lipase could be used for different oil conversion and preferred unsaturated fatty acids such as oleic acid to staturated fatty acids such as palmitic acid. The changes in concentration of fatty acids, diglycerides, and methyl esters in the reaction were studied and a mechanism of synthesis of biodiesel was suggested: the triglycerides are first enzymatically hydrolyzed into fatty acids, and then these fatty acids are further converted into methyl esters.     

微波辐射活性炭固载钨硅酸催化合成丙酸异戊酯

丙酸异戊酯是一种用途广泛的香料,为无色透明液体,具有浓郁的菠萝和洋梨果实香气,广泛用于涂料和食品工业.目前,国内外主要用浓硫酸催化酯化来合成[1].这个工艺虽然成熟,浓硫酸的催化活性较高,价廉易得,但其酸性很强,易引起副反应,严重的腐蚀设备和污染环境[2],所以研究一种新型、高效、绿色的催化剂是十分必要的.     

微波辐射下氯化锌催化纤维素转化为呋喃类物质的研究

以氯化锌作为溶剂和催化剂,利用微波辅助氯化锌降解纤维素,致使纤维素直接转化为5-羟甲基糠醛(5-HMF)和1-(2-呋喃基)-2-羟基-乙酮两种呋喃类物质。通过考察反应温度、反应时间、氯化锌用量、纤维素加入量、微波功率和加热方式等因素对其摩尔产率影响可知,在140 mL质量分数为69%的ZnCl₂溶液中,纤维素用量为1 g,反应温度为135 ℃,反应时间为5 min,微波功率为500 W时,5-羟甲基糠醛的摩尔产率达到19.4%,微波功率为600 W时,1-(2-呋喃基)-2-羟基-乙酮的摩尔产率达到12.0%。     

Synthesis of (+)-goniothalamin and its enantiomer by combination of lipase catalyzed resolution and alkene metathesis

(+)-Goniothalamin has been synthesized by lipase catalyzed resolution of (1E)-1-phenylhexa-1,5-dien-3-ol using vinyl acrylate as acyl donor followed by ring closing metathesis of the formed (1R)-1-[(E)-2-phenylvinyl]but-3-enyl acrylate. The unreacted alcohol from the resolution, (1E,3S)-1-phenylhexa-1,5-dien-3-ol, was esterified non-enzymatically, and used for synthesis of (−)-goniothalamin.     

微波加热和常规加热下功能化离子液体催化合成丁二酸二辛酯

分别在微波辐射和常规加热下,以具有丙烷磺酸基功能基团的离子液体为催化剂催化丁二酸和正辛醇 合成丁二酸二辛酯,考察了其阴、阳离子对催化剂活性的影响.相比常规加热,微波加热提高了反应效率,缩短了反应时间.以[ PyPS]HSO4为催化剂,研究了催化剂用量、醇酸比和反应时间对酯化率的影响.结果表明:当催化剂用量为丁二酸的3wt％,酸醇比(丁二酸∶正辛醇)1∶4,反应温度150℃,反应时间15 min,功率400W时,酯化率达到95.74％.此外,微波辐射下[PyPS]HSO4催化剂重复使用6次后活性没有明显降低,酯化率仍有93.58％.