Synthesis and characterisation of medium-sized ring systems by oxidative cleavage. Part 2: Insights from the study of ring expanded analogues

Variable temperature NMR analysis and computational methods have been used to develop a detailed understanding of the ¹H NMR spectra of a family of medium-sized ring containing compounds. The family consists of analogues containing 10-, 11- and 12-membered rings and in all cases the NMR spectra at room temperature showed a series of diastereotopic methylene signals despite the lack of a stereogenic centre in these systems. On repeating the NMR analysis at higher temperatures, all the signals coalesced for the 12-membered ring system consistent with full interconversion of ring conformers. This was not observed in the analogous 10- and 11-membered ring systems with the interchange of conformers remaining slow on the NMR timescale. However, 1D gs-NOESY/EXSY NMR experiments showed that in the smaller ring systems interconversion of diastereotopic protons did occur. Computational studies suggest that the dynamic process observed by NMR for the 10- and 11-membered rings systems is different from that observed in the 12-membered ring containing compound.     

The chemical reactivity of a known anti-psoriasis drug. Part 1: Further insights into the products resulting from oxidative cleavage

The oxidative cleavage of the known anti-psoriasis drug 1 to give 2 has been reported previously. Due to the importance of accessing medium-sized ring containing systems via oxidative cleavage, this reaction has been revisited revealing additional information about the structure of 2. Alternative reaction products were identified when the reaction was carried out in the presence of water. The conversion of 1 to 2 has also been carried out using ruthenium tetroxide. A detailed variable temperature NMR and computational study of the restricted rotation of the N-aryl ring in 2 is presented.     

黄酮类化合物结构修饰及抗肿瘤活性研究进展

我国天然药物和中药资源丰富,种类繁多,可作为先导化合物进行修饰以提高可成药性。其中,黄酮类化合物是自然界中一种常见的天然多酚类化合物,在抗肿瘤方面具有其独特的生物活性;对其进行结构修饰与改造,可提高黄酮类化合物的生物利用度和抗肿瘤活性。本文通过查阅并整理近几年国内外的黄酮类化合物的相关文献,对黄酮类化合物的母核位点进行结构修饰与改造所得的101个黄酮类衍生物及其抗肿瘤活性及作用机制进行综述,同时讨论了构效关系,以期为黄酮类衍生物的结构修饰和抗肿瘤研究提供参考和帮助。     

槽轮间歇机构优化设计

在分析了槽轮机构工作原理和设计中所存在的问题基础上，建立了数学模型，并对参数进行了优化设计，有效地解决了槽轮机构在运动过程中的不平稳性，最大限度的降低了冲击，为进一步和CAD系统的连接提供了有效途径。     

夸克—结模型与内含强子,反强子谱

本文应用从亚夸克理论获得的夸克——结模型,分析了强子碎片的强子、反强子谱的行为.碎片演化能由夸克或双夸克的级联衰变机制来实现。据此计算了质子碎片的某些内含强子、反强子谱的比,其结果令人满意并与实验相符。     

α—N原子稳定的碳负离子

详细讨论了酰氨，N－亚硝基化合物，异腈，脒，胺和硝基烷烃所生成的α-N原子稳定的碳负离子在有机合成化学中的应用，对部分反应的机理进行了阐述。     

石墨炉内石墨探针表面上的原子化机理研究 Ⅳ钒的原子化机理

本文通过X-射线衍射分析(XRD),扫描电子显微镜分析(SEM),化学分析光电子能谱分析(ESCA),并结合原子吸收测量,研究了钒在普通石墨管中石磨探针表面上发生的固相化学反应。结果表明,钒化合物在灰化阶段即可转化为热稳定性较高的碳化物,原子化的最后步骤为碳化物的热分解。     

红辉沸石合成A型分子筛的红外光谱研究

以天然红辉沸石合成了A型分子筛，通过XRD、IR光谱研究了其晶化过程。发现在1000-950cm^-1、750一600cm^-1、560cm^-1、460cm^-1处的红外吸收峰随结晶度有规律的变化，初步探讨其反应机理。     

大孔膦酸树脂吸附钇的研究

大孔膦酸树脂吸附钇的研究舒增年熊春华（丽水师范专科学校化学系浙江３２３０００）林峰（杭州大学化学系杭州３１００２８）关键词大孔膦酸树脂钇吸附机理中图分类号Ｏ６１４．３２２本文在ＨＡｃ－ＮａＡｃ体系中，研究了树脂吸附钇的性能及其机理，获得了诸多的结果，...     

双动压力机多连杆机构优化设计

本文论述闭式双动机械压力机外滑块八连杆机构优化设计时数学模型如何建立、优化方法怎样选择等问题。通过计算实例可以看出优化结果与维尔森公司计算结果的比较。