The stabilization of electrospun chitosan nanofibers by reversible acylation

Chitosan nanofibers fabricated by electrospinning are contaminated by acidic anions from the acid spinning solution, leading to instability of the nanofibers in aqueous solutions, and the traditional fiber treatment method will also lead to the deterioration of the nanostructure. Here we demonstrate a novel approach to removing the acidic anions with full preservation of the nanofibrous structure. The as-spun nanofibers are first protected (stabilized) by reversible acylation. Second, contaminants are then eliminated by hydrolysis; finally, acylation is reversed. Chemical analysis showed the removal of the acidic anions and the graft and removal of acyl groups. Morphological analysis showed that the reversibly acylated fibers had diameters <150 nm and nanofiber structure was maintained after immersion in aqueous solution. The membranes also were compatible with bone cells in culture. The resultant pure chitosan nanofibers show excellent stability in aqueous solution and exhibit broad potential in biomedical applications.     

Studies on the acylation of 4-(2-aminoethylthio)-7-nitrobenzofurazan: the role of bases in promoting the formation of fluorescent S-acyl derivatives through S-N Smiles rearrangement

The acylation of 4-(2-aminoethylthio)-7-nitrobenzofurazan has been investigated. Depending on the use of the base, a competitive Smiles rearrangement occurs during the acylation step leading to the formation of N-acyl and/or fluorescent S-acyl derivatives. The acylating agent also affects the ratio of N/S acylated isomers.     

Highly powerful and practical acylation of alcohols with acid anhydride catalyzed by Bi(OTf)(3).

Bi(OTf)(3)-catalyzed acylation of alcohols with acid anhydride was evaluated in comparison with other acylation methods. The Bi(OTf)(3)/acid anhydride protocol was so powerful that sterically demanding or tertiary alcohols could be acylated smoothly. Less reactive acylation reagents such as benzoic and pivalic anhydride are also activated by this catalysis. In these cases, a new technology was developed in order to overcome difficulty in separation of the acylated product from the remaining acylating reagent: methanolysis of the unreacted anhydride into easily separable methyl ester realized quite easy separation of the desired acylation product. The Bi(OTf)(3)/acid anhydride protocol was applicable to a wide spectrum of alcohols bearing various functionalities. Acid-labile THP- or TBS-protected alcohol, furfuryl alcohol, and geraniol could be acylated as well as base-labile alcohols. Even acylation of functionalized tertiary alcohols was effected at room temperature.     

Enhancements of Trifluoroacetic Acylated Five‐membered Heterocyclic Compounds Using as Additives in Dye Sensitized Solar Cells

In this study, five‐membered heterocyclic compounds are trifluoroacetic acylated for the purpose of providing more long pairs to enhance electrolyte in dye sensitized solar cells (DSSCs). Four five‐membered heterocyclic compounds will be trifluoroacetic acylated with trifluoroacetic anhydride by Friedel‐Crafts acylation: furan, thiophene, pyrrole and N‐methylpyrrole. The properties will be measured by cyclic voltage (CV), Fourier transform infrared spectroscopy (FTIR), solar simulator, and electrochemical impedance spectroscopy (EIS). We find out that furan and thiophene which we add in electrolyte as additives can increase short circuit current and photovoltaic efficiency, and furthermore, all the trifluoroacetic acylated heterocyclic compounds perform better photoelectric abilities than non‐trifluoroacetic acylated one. The photovoltaic efficiency will be increased from 4.439% to 5.197% when 1wt% trifluoroacetic acylated thiophene is added in electrolyte as additives.     

Acylation of novobiocin by carboxylic acid anhydrides: preparation and characterization of semi-synthetic novenamines

The acylation of novobiocin by carboxylic acid anhydrides leading to preparation of three families of semi-synthetic acylated novenamine analogues is reported. ESI-MS was used to monitor the reaction progress and enabled the isolation of intermediate compounds that provided insights into the sequence of acylation steps during the reaction. The chemoselectivity of the reaction depends on the carboxylic acid anhydride. The potential of the acylated novenamine analogues as leads for the development of antibacterial agents is discussed.     

Esters of heterocyclic γ-amino alcohols

Reduction of cis-3-cyano-4-hydroxypiperidines with lithium aluminum hydride (LAH) gave cis-3-aminomethyl-4-hydroxypiperidines, which were converted to cis-3-dimethylaminomethyl-4-hydroxypiperidines by methylation with formaldehyde and formic acid. Acylation of the methylated compounds with benzoyl and cinnatnoyl chlorides gave the corresponding esters. Condensation of cis-3-aminomethyl-4-hydroxypiperidines with formaldehyde gave perhydropyrido[3,4-e][1,3]oxazines, which were converted to 3-methylaminomethyl-4-hydroxypiperidines by means of LAH. The cis isomers of the corresponding O,N-diacyl derivatives of these amino alcohols were obtained by acylation with acetic anhydride and benzoyl and cinnamoyl chlorides.See [1] for communication V.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1363–1368, October, 1978.     

Preparation of p-[(S)(—)-2-phthalimidopropionyl] polystyrene

Samples of atactic and isotactic polystyrene were acylated with N-phthaloyl-L -alanyl chloride under the conditions of Friedel-Crafts reaction. The degree of acylation was strongly dependent on molecular weight, but not on the tacticity of polystyrene. Similarly the specific rotation of acylated polymers was not influenced by the structure of the polymer chain.     

N-甲基哌嗪作为环型二级胺在Stork反应中的应用

在Stork烯胺酰化反应中,通常需添加一个三级胺以中和反应中生成的氯化氢。产物常是液体或低熔点固体,不易提纯、析离。本文使用N-甲基哌嗪代替吗啉等常用的环状仲胺,考察其中的三级胺基能否起到外加三级胺的作用,并使酰化产物(Ⅲ)形成便于离析的盐酸盐结晶。我们以N-甲基哌嗪的环戊酮和环己酮烯胺为代表进行了乙酰化和苯甲酰化,析离了单酰基化产物Ⅲ(_a1),Ⅲ_a2和Ⅲ_b1及其相应的水解产物Ⅳ_a1,Ⅳ_a2,Ⅳ_b1和Ⅳ_b2;还得到了三个二酰基化产物。     

Nonaqueous biocatalytic synthesis of new cytotoxic doxorubicin derivatives: exploiting unexpected differences in the regioselectivity of salt-activated and solubilized subtilisin

Two enzymes, Mucor javanicus lipase and subtilisin Carlsberg (SC), catalyzed the nonaqueous acylation of doxorubicin (DOX). Compared to the untreated enzyme the rate of DOX acylation at the C-14 position with vinyl butyrate in toluene was 25-fold higher by lipase ion-paired with Aerosol OT (AOT) and 5-fold higher by lipase activated by 98% (w/w) KCl co-lyophilization (3.21 and 0.67 mumol/min g-lipase, respectively, vs 0.13 mumol/min g-lipase). Particulate subtilisin Carlsberg (SC) was nearly incapable of DOX acylation, but ion-paired SC (AOT-SC) catalyzed acylation at a rate of 2.85 mumol/min g-protease. The M. javanicus formulations, AOT-SC, and SC exclusively acylated the C14 primary hydroxyl group of DOX. Co-lyophilization of SC with 98% (w/w) KCl expanded the enzyme's regiospecificity such that KCl-SC additionally acylated the C4' hydroxyl and C3' amine groups. The total rate of DOX conversion with KCl-SC was 56.7 mumol/min g-protease. The altered specificity of KCl-SC is a new property of the enzyme imparted by the salt activation, and represents the first report of unnatural regioselectivity exhibited by a salt-activated enzyme. Using AOT-SC catalysis, four unique selectively acylated DOX analogues were generated, and KCl-SC was used to prepare DOX derivatives acylated at the alternative sites. Cytotoxicities of select derivatives were evaluated against the MCF7 breast cancer cell line (DOX IC50 = 27 nM) and its multidrug-resistant sub-line, MCF7-ADR (DOX IC50 = 27 muM). The novel derivative 14-(2-thiophene acetate) DOX was relatively potent against both cell lines (IC50 of 65 nM and 8 muM, respectively) and the 14-(benzyl carbonate) DOX analogue was as potent as DOX against the MCF7 line (25 nM). Activated biocatalysts and their novel regioselectivity differences thus enabled single-step reaction pathways to an effective collection of doxorubicin analogues.     

Studies on pyrazine. 23 . Homolytic acylation of 2-amino-3-cyanopyrazine and the related compounds with α-keto acids: A synthesis of 5-acyl-3-aminopyrazinecarboxylic acid derivatives

Homolytic acylation of 2-amino-3-cyanopyrazine (1) with α-keto acids led to the formation of 6-acylated compounds in 74-85% yields. Methyl 3-aminopyrazinecarboxylate (2) and 3-aminopyrazinecarboxamide (3) were also acylated under the same conditions although in lower yields. The observed reactivity of acylation is explained by comparison with the homolytic reactions of related pyrazines.     

Dual reactivity of 1,2-disubstituted dihydro-N-heteroaromatic systems. 8. Aromatization of N-acyl partly hydrogenated pyrazine and quinoxaline derivatives

N-mono- and N,N-diacyl 2,3-diindolyl-substituted 1,2-dihydro- and 1,2,3,4-tetra-hydropyrazines and quinoxalines were aromatized with triphenylmethyl perchlorate and 2,2,6,6-tetramethyl-1-oxo-piperidinium perchlorate. The hitherto unknown N-acylquinoxalinium perchlorates were obtained.For Communication 7, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 810–815, June, 1985.     

以环糊精为核的星形高分子合成及其温度、pH敏感性研究

以不同用量的氯乙酰氯与 β 环糊精反应 ,得到含有不同酰化度的氯乙酰化 β 环糊精 ,以此化合物为引发剂 ,采用原子转移自由基 (ATRP)引发甲基丙烯酸N ,N 二甲氨基乙酯 (DMAEMA)聚合 ,得到温度及pH敏感的以 β 环糊精为核的星形聚合物 .通过红外光谱、1 3C NMR、1 H NMR和氯元素滴定分析确定了酰化后的 β 环糊精的结构 ,并采用红外光谱、1 H NMR、元素分析、DSC表征了以 β 环糊精分子为核的星形聚甲基丙烯酸N ,N 二甲氨基乙酯的大分子结构 ,紫外光谱研究表明聚合物水溶液具有明显的温度和pH敏感性 .     

甲壳素类液晶高分子的研究Ⅱ-侧基长度和取代度对羧酰化壳聚糖的液晶性的影响

五种羧酰化壳聚糖即乙酰化、丙酰化、丁酰化、己酰化和庚酰化壳聚糖在二氯乙酸溶液中均呈现胆甾型溶致液晶相．临界浓度随侧基长度的增加而增加,但取代度（ 从０－２１ 变化到０－９４） 对临界浓度没有影响．在两相共存浓度区内,均呈现典型的滴状织构．从两相共存到完全液晶相的转变浓度也随侧基长度的增加而增加．     

Phase transfer catalyzed acylation

Sterically crowded phenols are conveniently acylated under phase transfer conditions. Selective 3-OH acylation of estradiol is accomplished by this method.     

Approach to the study of C-glycosyl flavones acylated with aliphatic and aromatic acids from Spergularia rubra by high-performance liquid chromatography-photodiode array detection/electrospray ionization multi-stage mass spectrometry

The use of mass spectrometry (MS) coupled to liquid chromatography (LC) as working tool for the study of the C-glycosyl flavones acylated with aliphatic and aromatic acids has allowed the tentative characterization of these compounds in Spergularia rubra and the establishment of the position of the acylation on the sugar moiety of the C-glycosylation by use of MS data. The combination of retention time (Rt), ultraviolet (UV) and MS(n) data of the compounds revealed their C-glycosyl flavone nature, being luteolin, apigenin and chrysoeriol derivatives. Ten non-acylated flavones were identified, from which six are described for the first time (one 7-O-glycosyl-6,8-diC-glycosyl flavone, four 6,8-diC-glycosyl flavones and one 2"-O-glycosyl-6-C-glycosyl flavone). Twenty-six acylated derivatives were also found for the first time. These compounds are grouped in three classes, namely, C-glycosyl flavones acylated with aliphatic acids, with aromatic acids or with a mixed acylation. The first group is characterized by the presence of one 6,8-diC-(acetyl)glycosyl flavone, four 6,8-diC-(malonyl)glycosyl flavones and two 7-O-glycosyl-6,8-diC-(malonyl)glycosyl flavones, while in the second one twelve 6,8-diC-(acyl)glycosyl flavones and two 7-O-glycosyl-6,8-diC-(acyl)glycosyl flavones are described. The last class contained five 6,8-diC-(malonyl,acyl)glycosyl flavones. No previous work has described the presence of C-glycosyl flavones acylated with aliphatic acids in this genus.     

Regioselective enzymatic acylation of troxerutin in nonaqueous medium

<正>A series of monosubstituted troxerutin esters have been synthesized by enzyme-catalyzed regioselective acylation of troxerutin in nonaqueous medium.Using divinyl dicarboxylates(CH_2=CH-OOC-(CH_2)_n-COO-CH=CH_2,n = 2,3,4,7,8,11) featuring different chain length as acyl donors and alkaline protease from Bacillus subtilis as catalyst,troxerutin was regioselective acylated at B' ethoxyl group.The results indicated that the regioselectivity of the enzyme-catalyzed acylation was not affected by the chain length of the acyl donor.     

Synthesis of Nickel(II) Azacorroles by Pd‐Catalyzed Amination of α,α′‐Dichlorodipyrrin NiII Complex and Their Properties

Synthesis of nickel(II) complexes of meso‐aryl‐substituted azacorroles was performed by Buchwald–Hartwig amination of a dipyrrin Ni^II complex with benzylamine through C? N and C? C coupling. The highly planar structure of Ni^II azacorroles was elucidated by X‐ray diffraction analysis. ¹H NMR analysis and nucleus independent chemical shift (NICS) calculation on Ni^II azacorrole revealed its distinct aromaticity with [17]triaza‐annulene 18π conjugation. In addition, acylation of azacorrole selectively afforded N‐ and C‐acylated azacorroles depending on the reaction conditions, showing the dual reactivity of azacorroles.     

Natural superabsorbent plastic materials based on a functionalized soy protein

A natural superabsorbent polymer (SAP) material based on an acylated soy protein was studied as a green alternative to non-biodegradable SAP. In order to obtain the natural SAPs, different amounts of succinic anhydride were used as acylating agent. Once the functionalized protein was obtained, it was mixed thoroughly with glycerol and then molded through a lab-scale injection molding device. Water uptake of samples obtained reached values much higher than those based on unacylated protein. Moreover, a greater extent of the acylation reaction led to higher water uptake values for the corresponding SAPs, probably related to their higher hydrophilic character. Water imbibing capacity measurements and thermogravimetrical analysis (TGA) seemed to confirm this. The presence of larger porous regions in acylated samples observed in SEM images could also play a role in their higher water uptake values.Furthermore, an increase in the extent of acylation reaction led to plastics with lower Young's modulus and higher extensibility.     

核糖核苷酸和核糖核苷的N-羧酰咪唑选样性酰化

应用N-羧酰咪唑在合适的条件下可按制备性规模进行选择性地酰化核糖核苷酸和核糖核苷, 得率为50-80%. 对反应机制作了初步探讨.     

在氯化亚锡存在下2,3-二甲基-2-丁烯与乙酐的催化酰化反应

一种新的催化剂,SnCl2·2H2O,已用于2,3-二甲基-2-丁烯与乙酐的酰化反应来制备高产率的3,3,4-三甲基-4-戊烯-2-酮 (TMP). 发现SnCl2·2H2O是室温下2,3-二甲基-2-丁烯与乙酐进行酰化反应的有效催化剂. 考察了催化剂用量、乙酐用量、反应时间和溶剂的加入等因素对该酰化反应的影响. 发现当催化剂/2,3-二甲基-2-丁烯摩尔比在0.30/1和 0.60/1之间、反应时间为2 h时,所得酰化产品的产率最高. 该酰化反应进行到完全所需的时间取决于催化剂用量和乙酐用量. 在需要加入溶剂的情况下,二氯甲烷或氯仿是一种合适的溶剂.