Computer-assisted analysis in organic synthesis

The planning of alternative routes for the synthesis of complex organic molecules has been facilitated by the formulation of guiding strategies that can be applied to a broad range of problems. Analysis of organic synthesis can be carried out in the retrosynthetic direction, opposite to the actual process of chemical synthesis, or bidirectionally, that is, as a combined retrosynthetic and synthetic search. An interactive computer program is described which utilizes the general strategies of retrosynthetic analysis and an appropriate database to generate pathways of chemical intermediates for chemical synthesis of a particular target structure. Computer graphics and standard chemical structures are used for man-machine communication.     

Acyclic stereocontrol through the aldol condensation

For the scientist who wishes to synthesize complex organic compounds, the most difficult problem is often establishing the correct configuration at the various chiral centers as the synthesis is being carried out. In the past decade, there has been an increasing effort to find direct solutions to this problem, which is particularly acute in the synthesis of acyclic and other conformationally flexible molecules. One of the oldest organic reactions, the aldol condensation, is emerging as a powerful tool for use in achieving such stereocontrol.     

Molecular recognition and metal ion template synthesis

Methods for the design and synthesis of ligands intended to be specific for a metal ion have been a recent chemical development. This article describes how this process can be inverted so that the specifics of the coordination environment around the metal ion can be used as a template in large-scale ligand synthesis. The synthesis of macrobicyclic ligands for ferric ion has been accomplished by using active esters of catechol ligands in which catecholate coordination to iron is a prelude to the organic chemical reactions that link the coordination subunits together into one ligand system surrounding a central metal ion coordination site. The lanthanide(III) ions, which are among the most labile metal ions known, have coordination numbers of 8 or higher, and thus their encapsulation into a macrobicyclic structure is a challenging problem. Lanthanide amine complexes have been used as metal templates in the synthesis of such macrobicyclic lanthanide complexes. There is evidence that such a complex is inert to exchange in aqueous solution.     

The 1979 nobel prize for chemistry

The 1979 Nobel Prize for Chemistry has been awarded jointly to Georg Wittig of the University of Heidelberg and Herbert C. Brown of Purdue University for their separate work in organic synthesis. Wittig's major achievement was the development of a highly specific method for the synthesis of olefins. Brown found major new routes to add substituents to olefins selectively. Both employed elements that had found little previous use in organic synthesis, and both prospered by following up on unexpected observations.     

Organic synthesis in Japan: from natural products to synthetic control

Organic chemistry in present day Japan, which has developed from early interest in natural products chemistry, now includes total synthesis, physical organic chemistry, synthetic methods, and organometallic chemistry. In this article, the current state of Japanese organic chemistry is briefly reviewed and a representative aspect of today's organic chemistry-exploration of new synthetic methodology-is discussed.     

Fluorous mixture synthesis: a fluorous-tagging strategy for the synthesis and separation of mixtures of organic compounds

The solution-phase synthesis of organic compounds as mixtures rather than in individual pure form offers efficiency advantages that are negated by the difficulty in separating and identifying the components of the final mixture. Here, a strategy for mixture synthesis that addresses these separation and identification problems is presented. A series of organic substrates was tagged with a series of fluorous tags of increasing fluorine content. The compounds were then mixed, and multistep reactions were conducted to make enantiomers or analogs of the natural product mappicine. The resulting tagged products were then demixed by fluorous chromatography (eluting in order of increasing fluorine content) to provide the individual pure components of the mixture, which were detagged to release the final products.     

二茂铁及其衍生物在医药领域应用的研究进展

近年来,对于二茂铁及其衍生物配位化合物的合成及其性能是金属有机化学研究的一个热点。本文不仅对二茂铁及其衍生物的性质、合成及其在医药领域的应用研究现状作了评述,并且对二茂铁及其衍生物在抗癌抗肿瘤、抗贫血、抗菌消炎和合成农药等方面做了归纳总结。此外,还简要概括了二茂铁及其衍生物的未来研究方向。     

崇明东滩不同演替阶段湿地土壤有机碳汇聚能力的差异性及其微生物机制

旨在阐明崇明东滩不同演替阶段湿地土壤有机碳汇聚能力的差异性及其机制,以期为优化湿地的管理与保育措施,进而保持和提升湿地的碳汇功能提供理论指导和决策依据。研究结果表明,4个不同演替阶段湿地土壤有机碳含量和微生物呼吸强度有显著差异(P<0.05),中高潮滩处的土壤有机碳汇聚能力最高,这是由于其具有较高的有机碳输入(植物枯落物)和相对较低的碳输出(土壤呼吸)。PCR-DGGE分析和系统进化树结果表明,4个不同演替阶段土壤的微生物群落结构存在差异,一些特异性优势菌的存在可能是影响土壤微生物呼吸强度,并最终影响土壤有机碳汇聚能力的重要原因。出现在高潮滩的噬纤维菌和假单胞属菌具有较高降解纤维素等有机质的能力,它们的存在可能强化了高潮滩的土壤呼吸作用,从而降低了高潮滩土壤的有机碳汇聚能力。     

New high-temperature Chiorella

Growth characteristics of Chlorella 1-9-30, a new strain of green, high-temperature algae, are compared with those of the widely used Chlorella 7-11-05. Under comparable conditions. Chlorella 1-9-30 has the same temperature range for growth as has Chlorella 7-11-05, but it generally has a higher growth rate. It also differs from Chlorella 7-11-05 morphologically. Because of its high capacity for organic synthesis, Chlorella 1-9-30 may be useful in biochemical, biophysical, and physiological research.     

纳米铜催化碳-氮偶联合成农药中间体研究

铜催化芳基卤代物与含氮化合物的偶联反应在当代有机合成中是极其重要的构建C-N键的方法。该研究通过溶剂热法制备片状、开口球及闭口球的纳米铜。对纳米铜催化C-N偶联反应体系进行优化改进,最佳反应条件为5 mol%催化剂、以氢氧化钾为碱、在二甲亚砜中反应24 h,最后在室温无配体条件下拓展了纳米铜催化C-N偶联反应的应用范围。     

自动灌装系统电液控制阀恒流调控软件包

针对ＤＹＦ多功能电液阀的工作原理及其特性曲线，建立了自动灌装系统的恒流调控模型。模型采用ＰＤ算法实现了电液控制阀的恒流调控，以Ｃ语言为工具开发了自动灌装系统ＤＹＦ型多功能电液阀恒流调控软件包，该软件包包括主程序或执行程序中，中断服务程序，采样和电磁阀调控程序。     

COMPARING PERFORMANCE OF CROP SPECIES MIXTURES AND PURE STANDS

•The literature on intercropping comprises thousands of papers. •Evidence synthesis is needed to develop general conclusions. •Quantitative evidence synthesis requires meaningful comparative performance metrics. •The background, meaning, and limitations of some performance metrics is explained. •Future challenges are identified. Intercropping is the planned cultivation of species mixtures on agricultural land. Intercropping has many attributes that make it attractive for developing a more sustainable agriculture, such as high yield, high resource use efficiency, lower input requirements, natural suppression of pests, pathogens and weeds, and building a soil with more organic carbon and nitrogen. Information is needed which species combinations perform best under different circumstances and which management is suitable to bring out the best from intercropping in a given production situation. The literature is replete with case studies on intercropping from across the globe, but evidence synthesis is needed to make this information accessible. Meta-analysis requires a careful choice of metric that is appropriate for answering the question at hand, and which lends itself for a robust meta-analysis. This paper reviews some metrics that may be used in the quantitative synthesis of literature data on intercropping.     

哈尔滨市渔村旅游开发初探

新农村建设是国家十一五规划的重点内容,渔村旅游作为新农村旅游的一种类型,开发有共性也有其独特性。通过分析哈尔滨市休闲渔业发展的实际情况及其存在问题,探讨了哈尔滨市渔村旅游规划开发的一些对策,并针对其作为湿地旅游一部分的开发,提出了一些方法。     

荷兰有机农业生产状况及启示

为探讨贵州有机农业生产的发展,采用收集二手资料、访谈以及参与式观察对荷兰的有机农业生产进行了调查研究。对荷兰的有机农业生产情况及社区支持型有机农场进行了介绍:政府对有机农业生产提供补贴,并建有专门的管理机构和学校。社区支持型有机农场把消费者看作是农场的重要组成成分,消费者参与农场的发展规划和各种活动,对农场的发展提出建议。笔者认为:贵州的有机农业生产应该考虑在学校中设立相关的培训课程,培养具有相关知识的学生;另可考虑发展社区支持型有机农场。     

Current status of asymmetric synthesis

In the last 30 years the subject of asymmetric synthesis has grown from a little studied academic niche in organic chemistry to an intensely investigated field of commercial importance and heightened general interest. Impressive advances have been made in several areas, notably catalytic asymmetric homogeneous hydrogenation, catalytic asymmetric epoxidation of allyl alcohols and stereochemical control of carbon-carbon bond-forming reactions. Asymmetric synthesis must now be deliberately considered along with other available methods as a practical strategy for the synthesis of any chiral compound.     

几种模拟酶的研究进展

模拟酶是一类利用有机化学方法合成的比天然酶简单的非蛋白分子.对环糊精模拟酶、冠醚化合物的模拟酶、超氧化物歧化酶模拟物等结构特征进行综述,为设计和合成更加简单、稳定的模拟酶提供参考.     

不同肥料对铁皮石斛生长的影响

[目的]筛选适合铁皮石斛大棚种植的施肥方案,促进铁皮石斛的生长,使其增产。[方法]在相同的大棚种植环境条件下,分别采用控释肥、海藻有机液肥、控释肥+有机液肥、水溶肥+有机液肥、不施肥对铁皮石斛进行处理,分别在7和10月对铁皮石斛的相关性状进行调查与分析。[结果]水溶肥+有机液肥、控释肥+有机液肥处理的成活率最高,铁皮石斛生长状况最好;不施肥处理成活率最低,长势最差。[结论]水溶肥+有机液肥是一种对铁皮石斛种植较好的施肥方案,但从节约成本和劳动力角度考虑,控释肥+有机液肥较理想,具有推广价值。     

微生物在农业废弃物堆肥应用中的研究进展

近年来,农业废弃物资源污染和浪费问题日趋严重,已经成为世界各国共同面临且亟需解决的问 题。利用微生物的氧化还原和合成能力,可将废弃物里有机质分解为腐殖质或合成有效态矿质元素,形成绿色、 稳定、安全的有机肥。堆肥化是实现农业废弃物无害化、减量化处理有效而经济的重要措施。而微生物是加快 有机固体废弃物分解速度的关键,是堆肥化处理重要的生物因子。简述了我国农业废弃物堆肥处理中的常用微 生物,堆肥处理技术,以及微生物在农业废弃物堆肥中的应用,并对农业废弃物堆肥应用中存在的问题进行探 讨和展望,针对我国农业废弃物资源化利用的发展趋势提出一些建议和方向,以期为我国农业废弃物资源化利 用提供一定的科学依据。     

Iron-catalyzed cyclopropanation in 6 M KOH with in situ generation of diazomethane

Diazomethane is a common and versatile reagent in organic synthesis whose broader use is generally impeded by its explosiveness and toxicity. Here we report that a simple iron porphyrin complex catalyzes the cyclopropanation of styrenes, enynes, and dienes under the demanding conditions [aqueous 6 molar potassium hydroxide (KOH) solution, open to air] necessary for the in situ generation of diazomethane from a water-soluble diazald derivative. A biphasic reaction medium arising from the immiscibility of the olefin substrates with water appears essential to the overall efficiency of the process. The work we describe highlights an approach to catalysis with untoward reactive intermediates, in which the conditions for their generation under operationally safe regimes dictate catalyst selection.     

有机砷制剂残留分析的研究进展

有机砷制剂是一种抗菌、促生长类的有机合成兽药,常被用作饲料添加剂,长期使用该种兽药的动物,其组织器官中将蓄积含砷类药物,并通过食物链的作用,危害人体健康。以3-硝基4-羟基苯砷酸、对氨基苯砷酸等主要有机砷制剂作为研究对象,从前处理方法、仪器检测方法等方面较为全面地概括了国内外有机砷制剂残留的研究进展;深入探讨了兽药分析技术的创新手段及发展趋势,以期为日后快速、准确、绿色地分析痕量兽药残留提供更多方法和思路。