手性双噁唑啉配体在不对称合成中的应用

双噁唑啉手性配体已广泛用于不对称Henry反应、环丙烷化反应、Aldol反应、烷基化反应、环加成反应中,并表现出很高的对映选择性和催化活性,成为最有用的手性配体之一。文章综述了近10年来双噁唑啉手性配体及高分子受载手性双噁唑啉在不对称合成中的研究进展。     

在不对称氮杂环丙烷化中双噁唑啉配位空间大小对对映选择性的影响

手性双噁唑啉是在不对称催化中广泛应用的一类重要的配体. 合成了一系列具有刚性骨架和不同配位空间的手性双噁唑啉配体, 并研究了在不对称氮杂环丙烷化反应中对对映选择性的影响, 结果表明通过调节配位空间的大小不仅可以改变对映选择性, 甚至还可以彻底改变对映面选择性. 研究结果还表明除通过改变配体手性中心的构型, 调节配体配位空间也可以改变催化剂的对映面选择性.     

手性双(口恶)唑啉配体-金属配合物在催化不对称环丙烷化反应中的应用研究进展

将用于催化不对称环丙烷化反应中的手性双(口恶)唑啉配体按相应羧酸母体骨架分为丙二酸类,酒石酸类,吡啶二羧酸类,联苯、联萘及双核二茂铁类,将聚合物支载的双(口恶)唑啉配体单独进行了讨论.对各类配体的最新研究进展及其金属配合物在不对称环丙烷化反应中的应用作了总结.     

轴不稳定手性配体的开发及其在不对称催化反应中的应用

轴不稳定配体应用于不对称催化有其独到的特点, 不同于传统的轴稳定手性配体. 综述了轴不稳定的噁唑啉、双膦、单膦、双羟基及N—O等配体的开发及其在不对称催化中的应用.     

手性双齿氮配体2,2＇-双噁唑啉的合成及应用

近十年来,手性二氮配体的发展迅速,并已被成功地用于双羟基化反应,Aldol 反应,硅氢化反应等不对称合成.鉴于噁唑啉配体在一些不对称合成反应中的优异表现,以及我们对于具有 C_2对称性的双齿氮配体的兴趣,我们设计合成了一类新型的、具有 C_2对称性的手性双齿氮配体——(4S,4′S)-4,4′-二取代-2,2′-双噁唑啉1,并研究了它们在双羟基化反应中的不对称诱导作用.手性配体1的合成如下式所示:     

手性pybox-金属络合物及其在不对称催化反应中的应用

具有C2对称性的双噁唑啉型吡啶(pybox)是一类有效的手性配体,能与许多金属离子配位,其手性催化性能已得到越来越多的关注。本文综述了手性配体pybox和pybox-金属络合物的合成方法,特别是近年来pybox-金属络合物在不对称催化反应如不对称环丙烷化反应、不对称Diels-Alder反应、1,3-偶极环加成反应、不对称aldol反应等中应用的最新进展。     

手性双唑啉铜配合物在不对称合成中的应用

综述了手性双E唑啉配体的主要结构类型,并讨论了手性双E唑啉铜配合物在不对称Diels-Alder反应、Ene反应、Mukaiyama adol反应、烯丙基氧化、环丙烷化、氮杂环丙烷化等反应中的应用。     

噁唑啉类配体在钯催化烯烃的不对称氧化官能化反应中的应用

钯催化烯烃的官能化反应是实现简单烯烃向复杂分子转化的高效方法之一,尤其是烯烃的氧化官能化反应,能够更加高效地得到烯烃的双官能化的产物,其不对称反应也受到化学家们的广泛关注.但是在氧化双官能化反应中,要求手性配体能够耐氧化.近年来的研究表明,噁唑啉配体在这类反应中是能够兼容的,而且可以得到优秀的对映选择性.本综述介绍了近期噁唑啉配体在钯催化烯烃的氧化官能化反应中的应用进展.     

双噁唑啉接枝的氨基酸聚合物作为手性催化中心在不对称Henry反应中的应用

通过控制聚合单体L-谷氨酸-γ-乙酯和DL-半胱氨酸以及聚合过程中引发剂与单体的比例,制备了一系列溶解性能不同的氨基酸聚合物.利用其作为负载手性配体的载体,通过双噁唑啉配体上的双键和聚合物上巯基的加成反应,合成了一系列双噁唑啉接枝氨基酸聚合物.将合成的聚合物作为可回收的手性催化剂用于催化不对称Henry反应,反应选择性(e. e.值)在50%～90%之间,产率在67%～95%之间.该催化剂可以循环使用至少7次而不需要经过重新活化.     

镁-双噁唑啉络合物催化3,5-二甲基-N-α,β-不饱和酰基吡唑的不对称共轭氰化反应研究

报道了镁-双噁唑啉络合物体系催化的TMSCN与3,5-二甲基-N-α,β-不饱和酰基吡唑的不对称共轭氰化反应.考察了BOX配体结构、配体与金属比例、温度、溶剂等对反应的影响.研究结果表明,使用双苄基取代的双噁唑啉配体与二丁基镁(物质的量比为2;1)在1,2-二氯乙烷中原位生成手性催化剂,催化剂用量为10 mol％,反应...     

Near-infrared spectroscopy of autunites

NIR spectroscopy has been applied to the study water in the interlayer of the autunite minerals. The spectra of autunites and metaautunites in the first HOH fundamental overtone are different and the spectra of autunites of different origins in the 6000-7500 cm(-1) region are considerably different. A number of conclusions are made based upon the NIR spectra: (a) The spectra of different autunites are different in the NIR spectral region; (b) the spectra of metaautunites show similarity; (c) the spectra of metaautunites are different from that of autunites. NIR spectroscopy provides a method of determination of the structure of water in the interlayer of natural autunites. The implication from the variation in the NIR spectra is that the structural arrangement of water for different autunites is different and is sample dependent. NIR spectroscopy has a wide potential for the study of the autunite minerals.     

Determination of protein-bound trace elements in human cell cytosols of different organs and different pathological states

In the human body, there exists over 200 different cell types, which differ in size and structure and have specialised functions in the organism. Therefore it can be assumed that these different cells also contain different proteins necessary to carry out the respective specialised functions. This supposed different metalloprotein composition in different human organs cannot be demonstrated by determination of total element concentrations. Therefore investigations of the different protein-bound forms of the elements were achieved by speciation analysis: The biomolecules were separated by size exclusion chromatography and the elements detected on-line in the eluate by a hyphenated inductively coupled plasma mass spectrometer (ICP-MS). For the interpretation of the obtained element profiles, an identification of the signals and their assignment to different metalloproteins was necessary. This identification was carried out by means of specific protein assays, i.e. enzymatic assays or immunochemical reactions, in collected fractions of the chromatographic separations. A comparison of the element binding pattern in cytosols of different human organs was then possible. The optimised method was applied to tissue cytosols of different human organs. As expected, the element patterns varied for different organs of the same patient and for the same organ of patients with different diseases. Metalloproteins and their bound metals could consequently be considered as biological markers for physiological differences or pathological changes in human tissues.     

Ancient Roman wall paintings mapped nondestructively by portable NMR

The stratigraphies of decorated walls in ancient Herculaneum, Italy, were analyzed by single-sided ¹H NMR. A large version of the NMR-MOUSE® with a maximum penetration depth of 25 mm was used to map proton density profiles at different positions of the Mosaic of Neptune and Amphitrite showing considerable differences between different tesserae and the mortar bed at different times of the year. In the House of the Black Room, different mortar layers were observed on painted walls as well as different proton content in different areas due to different moisture levels and different conservation treatments. The proton density profiles of the differently treated areas indicated that one method leads to higher moisture content than the other. Untreated wall paintings from different times were profiled in a recently excavated room at the Villa of the Papyri showing two different types of mortar layer structures which identify two different techniques of preparing the walls for painting. Reflectance Fourier mid-infrared spectroscopy and in situ X-ray fluorescence measurements complemented the NMR measurements and provided additional insight into the identification of organic coatings as well as the nature of the pigments used, respectively. The information acquired nondestructively by NMR is valued for elaborating conservation strategies and for identifying different schools of craftsmen who prepared the mortar supports of the wall paintings.     

Laser defocusing effects on laser ablation inductively coupled plasma-atomic emission spectrometry: different ablation interactions between the laser and low-alloy steel, Fe pellets, and a pond sediment pellet.

The ablation interaction between a laser and solid samples, which affects the analytical performance for laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES), was studied. The emission intensities of elements observed by LA-ICP-AES (LA-ICP-AES element signal intensities) for different solid samples were measured under different laser defocusing conditions with a fixed laser output energy. It was found that the optimum laser defocusing conditions were dependent on the different solid samples with different sample characteristics, and also on the different elements with different elemental characteristics in each solid sample. A low-alloy steel, pellets containing different Fe concentrations (0 - 100% Fe pellet), and a pond sediment pellet were used as different solid samples. The variations of the LA-ICP-AES Fe signal intensities observed under different laser defocus conditions were completely different between the low-alloy steel and the pond sediment pellet. The changes in the LA-ICP-AES Fe signal intensities for 90 and 100% Fe pellets were similar to that of the low-alloy steel. However, pellets with lower Fe concentrations (less than 70%) showed different trends and the defocusing behavior became closer to that of the pond sediment pellet. The LA-ICP-AES signal intensities of other elements were also evaluated, and were compared for different solid samples and different defocusing behavior. It was observed that the changes in the LA-ICP-AES signal intensities of almost all elements in the pond sediment pellet showed a similar trend to those of Fe for different laser defocus positions; that is, the elemental fractionation for these elements in the pond sediment pellet seemed to be relatively small. On the contrary, it was found that the LA-ICP-AES Si, Ti, and Zr signal intensities for low-alloy steel showed different trends compared to those of other elements, including Fe, under different defocusing conditions; that is, the elemental fractionation observed for the low-alloy steel was larger than that of the pond sediment pellet. From these results, different ablation interactions between the laser and the different solid samples were considered, and attributed to the sample characteristics, such as the matrix, hardness, and conductivity. Elemental fractionation was attempted to be explained by using elemental characteristics, such as the melting point and ionization energy of the elements.     

不同环境条件对土壤-巴戟天系统重金属分布的影响

采用AA-6800型石墨炉原子吸收光谱仪研究了土壤-巴戟天系统中铅的分布情况,包括不同地段、不同土壤类型、不同土壤pH值对土壤-巴戟天入药部位根和果实中铅的含量影响。实验结果表明,环境条件变化对土壤-巴戟天系统铅含量有一定的影响,其中土壤的pH值对土壤中的有效铅浓度及巴戟天的铅含量影响较大。     

Design of open-framework germanates by combining different building units

Open-framework germanates with extra-large channels are built from two different types of clusters. The two different clusters are connected in such a way to form a pseudo-body-centered cluster aggregate (PBCCA). The different packing of PBCCAs resulted in different 3D open-framework germanates.     

溪黄草根茎叶微量元素含量的测定

用等离子体原子发射光谱法对溪黄草根、茎、叶等不同部位微量元素的含量进行了测定,溪黄草不同部位都含有18种微量元素,其不同部位微量元素分布有共同之处,也存在明显的差别。     

Process dependence of pressure-specific volume-temperature measurement for amorphous polymer: Acrylonitrile-butadiene-styrene

The process dependence of pressure-specific volume-temperature (pvT) measurement for an amorphous polymer, acrylonitrile-butadiene-styrene (ABS), was investigated. The influences of different measurement processes (heating, cooling, compression, and decompression with different rates) were considered in the pvT measurements. The pvT measurements of isobaric cooling and heating with different cooling and heating rates (2, 5, and 10 °C/min) and isothermal compression and decompression with different compression and decompression rates (up to 920 bar/s) were conducted. The testing temperature ranged between 40 and 230 °C and the pressure ranged between 20 and 2200 bar. The obtained results demonstrated that the pvT diagram will be significantly different depending on the direction in which the pressure or temperature is changing and also on the rate of the change. Isobaric pvT diagrams are different between cooling and heating. Fast cooling accelerates phase transitions, while fast heating reverses. Specific volume at the same pressure and temperature in decompression process is lower than that in compression. Compression and decompression leads to different pvT curves. Compression and decompression rates have different effects on specific volume in different states.     

宁夏枸杞甜菜碱提取物高效液相色谱指纹图谱研究

建立宁夏枸杞甜菜碱提取物高效液相色谱指纹图谱,为鉴别不同来源的宁夏枸杞提供依据。以10批宁夏不同产地的宁夏枸杞主栽品种"宁杞Ⅰ号"样品建立枸杞甜菜碱提取物指纹图谱共有模式,采用"中药色谱指纹图谱相似度评价系统"软件进行数据处理,对15批不同来源的枸杞样品进行了分析。结果表明:8个特征峰构成了宁夏枸杞甜菜碱提取物的色谱指纹图谱,不同产地、不同品种的枸杞样品甜菜碱提取物指纹图谱存在差异;建立的枸杞甜菜碱提取物高效液相色谱(HPLC)指纹图谱对不同产地、不同品种枸杞的鉴别有参考价值。     

Chemical space sampling by different scoring functions and crystal structures

Virtual screening has become a popular tool to identify novel leads in the early phases of drug discovery. A variety of docking and scoring methods used in virtual screening have been the subject of active research in an effort to gauge limitations and articulate best practices. However, how to best utilize different scoring functions and various crystal structures, when available, is not yet well understood. In this work we use multiple crystal structures of PI3 K-γ in both prospective and retrospective virtual screening experiments. Both Glide SP scoring and Prime MM-GBSA rescoring are utilized in the prospective and retrospective virtual screens, and consensus scoring is investigated in the retrospective virtual screening experiments. The results show that each of the different crystal structures that was used, samples a different chemical space, i.e. different chemotypes are prioritized by each structure. In addition, the different (re)scoring functions prioritize different chemotypes as well. Somewhat surprisingly, the Prime MM-GBSA scoring function generally gives lower enrichments than Glide SP. Finally we investigate the impact of different ligand preparation protocols on virtual screening enrichment factors. In summary, different crystal structures and different scoring functions are complementary to each other and allow for a wider variety of chemotypes to be considered for experimental follow-up.