室温条件下“一锅多组分”脯氨酸催化合成N,O-缩醛化合物

以芳香醛、脲和醇为原料,过量的醇为溶剂, D-脯氨酸为催化剂,开发了一种简单的多组分一锅法合成N,O-缩醛化合物的方法.在室温下反应30 h后,以良好的收率合成了一系列N,O-缩醛化合物.     

由α-羰基一硫代半缩醛合成含氮杂环化合物

利用α-羰基一硫代半缩醛和含氨基的化合物反应,合成了六员含氮杂环化合物,其结构通过红外、核磁、质谱和元素分析得到了证实.     

酰胺缩醛法合成N,N,N＇-三取代甲脒的研究

脒类化合物用作杀螨、杀虫剂,除草剂,消炎剂等[1,2],也是合成氮杂环化合物的中间体[3].有关脒的合成及应用研究的进展,我们已进行了较为详细的评述[4].早期的合成方法有亚酯胺解法,异腈胺解法和三氯氧磷法[5].我们采用DMF二烷基缩醛,在温和的反应条件下,合成出了N,N,N'-三取代甲脒,产率达90%左右,产物分离简便,除去副产物醇后,得到纯度较高的产物.酰胺缩醛具有较高的反应活性,用其可以合成出其它方法无法得到的脒.因此,酰胺缩醛法操作简便,适用范围广泛,是合成N,N,N＇-三取代甲脒较为理想的方法.     

铟粉促进下“一锅法”合成α-亚甲基-γ-三氟甲基-γ-丁内酰胺化合物

探索了铟粉促进下,三氟乙醛甲基半缩醛或三氟苯乙酮与酰肼、2-(溴甲基)丙烯酸乙酯的"一锅法"反应,得到了一系列α-亚甲基-γ-三氟甲基-γ-丁内酰胺化合物.该方法使用价廉易得的三氟乙醛甲基半缩醛或三氟苯乙酮作为三氟甲基合成砌块,反应条件温和、产率高、操作简单,为合成含三氟甲基的α-亚甲基-γ-丁内酰胺化合物提供了一种新方法.     

二丁基锡(IV)磺酸酯催化合成缩醛(酮)

用二丁基氧化锡与苯磺酸、甲磺酸反应制备了两种新的有机锡化合物——二丁基锡(IV)磺酸酯. 以二丁基锡(IV)磺酸酯作催化剂, 合成了一系列缩醛(酮), 并通过正交实验, 优化了有机锡催化缩醛(酮)合成反应的反应条件. 实验表明该催化反应产率高, 反应时间短, 催化剂用量少且能回收再利用.     

环缩醛化合物在光聚合体系中的研究进展

环缩醛化合物作为一类具有光敏性的化合物,虽然在上世纪60年代有较多的研究,但由于其吸收波长较窄、引发效率较低等限制,后期研究比较少.但最近5年内,由于对胡椒环等环缩醛化合物的重新认识,尤其是将其作为光聚合引发助剂来提高引发效率或减少引发体系的毒性,获得了光聚合生物材料领域的特别关注.本文对环缩醛类化合物的光聚合行为进行了系统阐述,对当前环缩醛类化合物用作光引发剂及助引发剂的进展也进行了详细介绍.     

烯酮二硫代缩醛类化合物合成方法改进

烯酮二硫代缩醛类化合物在杂环化合物合成方面有着极为广泛的用途[1],而此类物质的合成通常是在强碱性条件下进行,如NaH,RONa,NaOH,KOH等.这对于一些对碱敏感的化合物的合成比较困难.我们曾发现[2～4],在无水磷酸钾存在下,伯胺或仲胺与二硫化碳和卤代烃在室温下一锅煮反应可以高收率得到氨基二硫代甲酸酯.为进一步研究和拓展该方法的适用范围,我们试图将该方法应用于烯酮二硫代缩醛类化合物的制备中.研究发现,用无水磷酸钾代替原法中的强碱,不同的活泼亚甲基化合物与二硫化碳和卤代烃可在室温下快速反应.结果表明,该方法具有反应时间短、反应条件缓和、收率较高等优点.     

Fe(OTf)3催化含有N,O-缩醛结构硼酸酯的合成研究

报道了一种Fe(OTf)₃催化含有N,O-缩醛结构硼酸酯的简便合成方法,反应过程历经路易斯酸催化亚胺鎓与有机硼酸室温进行加成反应,以58%～98%的收率生成了一系列N,O-缩醛硼酸酯化合物.实验结果表明产物具有硼酸酯的性质,可以进行偶联反应.     

含吡啶亚甲基的S,N-烯酮缩醛的合成及生物活性

合成了含吡啶亚甲基的氰基、酯基或双氰基S,N-烯酮缩醛化合物．应用X射线衍射方法确定了目标化合物为E构型．生物活性测定表明,该类化合物具有很高的除草活性,并且对农作物表现出优良的选择性．     

手性缩醛的催化不对称合成研究进展

缩醛是许多药物和天然产物分子中常见的结构单元,研究发现手性缩醛的生物活性通常优于其消旋体.由于手性缩醛存在消旋化倾向,其催化不对称合成具有挑战性,近年来才引起关注.综述了目前手性N,N-缩醛、N,O-缩醛、N,S-缩醛、O,O-缩醛的催化不对称合成研究进展,及其在含缩醛骨架手性药物合成中的应用.     

Analytical strategies to determine antibiotic residues in fish

The accelerated growth of aquaculture has resulted in a series of harmful effects to human health. The widespread and unrestricted use of antibiotics in this industry, to prevent bacterial infections, leads to remaining amounts in the aquatic environment. This has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase in antibiotic resistance in fish pathogens as well as in the transfer of these resistance determinants to human pathogens. Moreover, the use of large amounts of antibiotics may lead to the presence of residual antibiotics in fish tissue and fish products. Fluoroquinolones, tetracyclines, penicillins, sulphonamides and other antibiotics, exhibiting activity against both Gram-positive and Gram-negative bacteria, are widely used for the treatment and prevention of diseases in fish. An extended and comprehensive review on the recent analytical methodologies concerning antibiotic residues in fish reported in the literature is provided in the present article. Emphasis is given on sample preparation regarding isolation and purification, chromatographic conditions and method validation according to legislation. Results of published assays are comparatively presented and criticised.     

Calibration methods for microdialysis sampling in vivo: muscle and adipose tissue

Calibration methods for microdialysis sampling were studied in the muscle and adipose tissue of rats. Both the delivery method and the no-net-flux method were used to determine the extraction efficiency (EE) of acetaminophen and caffeine in both tissues. There was no concentration dependence of the EE either in vitro or in vivo for either acetaminophen or caffeine. The EEs determined by the delivery and no-net-flux methods were not different. However, the EEs of both caffeine and acetaminophen determined in vitro were significantly higher than those determined in the muscle and adipose. This indicates that mass transfer in the tissue is the rate-determining factor for the EE in vivo. The relative difference between the EE in vitro and the EE in the muscle was smaller than the difference between the EE in vitro and the EE in the adipose. In addition, the EE in the muscle decreased more than the EE in the adipose after the animal was euthanized. This indicated that exchange between the extracellular fluid and plasma is the rate-determining step in mass transport relative to microdialysis sampling. This has a more significant effect on the EE in the muscle than the EE in the adipose. Both the delivery and no-net-flux methods can be used to calibrate microdialysis probes in the muscle and adipose.     

Evaluation of the Fate of Aldicarb and Its Metabolites in Oranges

Abstract

The accumulation, persistence and fate of systemic pesticide aldicarb was melencholy evaluated in orange crops. The concentration of this pesticide and its two toxic metabolites, aldicarb sulfoxide and aldicarb sulfone was determined in leaves, rind and pulp of three orange varieties (Satsuma, Navelina and Clemetina de Nules) and in the top soil of the orange groves. The groves were located in two different places in the Valencia Community (Spain). The analysis showed that the aldicarb concentration was lower than those of aldicarb sulfoxide and aldicarb sulfone. In all cases, the residues persisted at least 160 days in vegetable samples and between 157 and 227 days in soil samples. Residue concentrations measured in the soil samples were highly variable but a relation with the organic matter content can be observed. The residue levels found in vegetal products were higher in leaves than in rind, and in rind than in pulp. The maximum residue values were obtained between 47 and 70 days after the application. One hundred days after treatment (Security period) the residue levels of total fruit were lower than the maximum residue level of 0.2 mg/kg established by law.     

Changes in density and surface tension of water in silica pores

 The density and surface tension of water in small pores of silicas have been investigated. These physical properties of water in the pores were calculated from a comparison of pore volumes and pore radii which were estimated from adsorption and desorption isotherms of nitrogen and water. Below a pore radius of about 5 nm both the density and the surface tension of water in the pores were smaller than those of the bulk liquid and decreased with a decrease in pore size. The density of water in the pores decreased with an increase in the concentration of surface hydroxyl groups. Similarly the surface tension of water in the pores is influenced by the surface hydroxyl groups. Anomalous changes in the density and surface tension of the water in the pores are attributed to the interaction of water molecules with surface hydroxyl groups and hydrogen-bond formation among water molecules. Received: 20 April 1999 Accepted in revised form: 17 November 1999     

Liquid chromatography-tandem mass spectrometric analysis and regulatory issues of polar pesticides in natural and treated waters

Pesticides are among the most detected contaminants in the aquatic environment. This is mainly due to their use in agriculture and their physico-chemical properties that enable transportation and a persistent or pseudo-persistent existence in the water media. Several directives and guidelines set maximum levels of pesticides in water in order to protect the human and environmental health. A brief discussion of the existing directives and guidelines concerning pesticides in water is presented, e.g., the new regulatory framework for the Registration, Evaluation and Authorisation of Chemicals (REACH), and the Directive 91/414/EEC concerning the placing of plant protection products on the market. Up-to-date analytical tools to support the REACH program are of prime importance to ensure its complete implementation. Since liquid chromatography (LC) coupled to mass spectrometry (MS) is considered the most appropriate technique for determination of most modern pesticides in environmental waters, the most recent developments and applications in this field are discussed in detail in this review.     

沱江流域Pb、Cd的环境污染化学行为研究

对沱江流域金堂、简阳、内江三地河流沉积物中重金属Pb和Cd含量及其时空分布特征进行了研究,并结合与沉积物中Fe、Mn和LOI等参数的相关性对河流沉积物中Pb和Cd地球化学性质进行了初步的分析和讨论。结果表明,沱江三地沉积物中Cd、Pb含量不高,平均含量按上、中、下游次序逐渐降低;从垂向分布行为看,Cd在上游金堂地区上部含量高于下部,而中、下游两地则相反,而Pb均随着深度的增加而减少,反映了近年来人类活动所产生Pb污染的加剧;TOC、沉积物性状和上覆水体中的物化性质对于其垂向分布有着较大影响。对于深入揭示水环境中重金属的环境地球化学循环有着重要的指导意义。     

中性溶质在反相毛细管电色谱中的保留行为

分别在以甲醇、乙腈、异丙醇和四氢呋喃为有机改性剂的４种二元流动相体系中对中性溶质在反相毛细管电色谱中的保留行为进行了研究。不仅考察了有机改性剂的种类和浓度对电渗淌度的影响,而且建立了溶质容量因子与有机改性剂在流动相中体积分数间的定量关系,此外还对样品在反相毛细管电色谱和反相毛细管高效液相色谱中的保留行为进行了比较,发现中性溶质在这两种分离模式中的容量因子基本相同。     

ESR方法检测竹红菌素的半醌负离子自由基

从顺磁共振波谱检测到通过竹红菌素的光诱导还原和基态竹红菌素跟脂肪胺的电子转移两条途径所得到的自由基信号, 并由电化学还原得到同一自由基, 确认它为半醌负离子自由基。竹红菌素溶液中加入芳香胺观察不到ESR信号。它的3,10位上与醌基相邻近的羟基离解以后, 无论在基态还是在激发态都观察不到ESR信号。此外, 还从吸收光谱观察到半醌负离子自由基吸收以及竹红菌素跟脂肪胺之间的相互作用。     

Antioxidative effects of flavonols and their glycosides against the free-radical-induced peroxidation of linoleic acid in solution and in micelles

The antioxidative effect of flavonols and their glycosides against the peroxidation of linoleic acid has been studied in homogeneous solution (tBuOH/H(2)O, 3:2) and in sodium dodecyl sulfate and cetyl trimethylammonium bromide micelles. The peroxidation was initiated thermally by the water-soluble initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and the reaction kinetics were studied by monitoring the formation of linoleic acid hydroperoxides. The synergistic antioxidant effect of the flavonols with alpha-tocopherol (vitamin E) was also studied by following the decay kinetics of alpha-tocopherol and the alpha-tocopheroxyl radical. Kinetic analysis of the antioxidative process demonstrates that the flavonols are effective antioxidants in solution and in micelles, either alone or in combination with alpha-tocopherol. The antioxidative action involves trapping the initiating radicals in solution or in the bulk-water phase of the micelles, trapping the propagating lipid peroxyl radicals on the surface of the micelles, and regenerating alpha-tocopherol by reducing the alpha-tocopheroxyl radical. It was found that the antioxidant activity of the flavonols and their glycosides depends significantly on the position and number of the hydroxy groups, the oxidation potential of the molecule, and the reaction medium. The flavonols bearing ortho-dihydroxy groups possess significantly higher antioxidative activity than those without such functionalities, and the glycosides are less active than their parent aglycones. The activity of the flavonols is higher in micelles than in solution, while the activity of alpha-tocopherol is lower in micelles than in solution. This is because the predominant factor for controlling the activity is the hydrogen-bonding interaction of the antioxidant with the micellar surface in the case of hydrophilic flavonols, while it is the inter- and intramicellar diffusion in the case of lipophilic alpha-tocopherol.