A New Perylenequinone from Hypomyces sp.

Some metabolites of fungi and plants containing perylenequinones have been used as folk medicine for the treatment of many diseases1,2. A filamentous fungus, Ascomy-cetes Hypocreaceae Hypomyces (Fr.) Tul. sp., was found from the northwestern mountains of Yunnan Province, and cultured successfully in the laboratory. A new perylenequinone, named hypomycin A (1), was isolated from its mycelia. In this paper the structure elucidation of 1 was described. Figure 1 The structure of compound 1 Fig…     

Investigations on the adsorbents for uremic middle molecular toxins (II)

Chitosan resins, which clinically served as adsorbents in hemo perfusion therapy, were prepared with reversed-phase suspension methodology using three differently structured crosslinking agents, methanal, glyoxal and glutaraldehyde. And the glyoxal and glutaraldehyde crosslinked chitosan resins were reduced with NaBH₄ afterwards. By analyzing the results from FTIR and SEM, it was found that the reduction treatment to the adsorbents efficiently improved the chemical stability of these chitosan resins, and the shifts in crosslinking agents exerted influences over the morphologies of the adsorbents obviously. After being put to use in the adsorption tests upon some model uremic middle molecular toxins and BSA in vitro, all three adsorbents demonstrated a fairly realistic adsorption capability to the model toxins but little to BSA. And the adsorption process reached the equilibrium in a clinically qualified short time. But the adsorption capacities of these adsorbents to the model toxins were quite different. It had been found that with the growing of fatty chain length of crosslinking agent, these adsorbents showed a gradually increased adsorption capacity to the model toxins, and the glutaraldehyde crosslinked chitosan resin behaved best.     

Cross‐Linked Aptamer–Lipid Micelles for Excellent Stability and Specificity in Target‐Cell Recognition

The specific binding ability of DNA–lipid micelles (DLMs) can be increased by the introduction of an aptamer. However, supramolecular micellar structures based on self‐assemblies of amphiphilic DLMs are expected to demonstrate low stability when interacting with cell membranes under certain conditions, which could lead to a reduction in selectivity for targeting cancer cells. We herein report a straightforward cross‐linking strategy that relies on a methacrylamide branch to link aptamer and lipid segments. By an efficient photoinduced polymerization process, covalently linked aptamer–lipid units help stabilize the micelle structure and enhance aptamer probe stability, further improving the targeting ability of the resulting nanoassembly. Besides the development of a facile cross‐linking method, this study clarifies the relationship between aptamer–lipid concentration and the corresponding binding ability.     

B(C6F5)3催化的醛与烷氧基羟胺的一锅法还原胺化反应

近年路易斯酸B（C₆F₅）₃催化的醛酮还原及胺化反应研究表明,缺电子的路易斯酸B（C₆F₅）₃也可以作为一种"耐水"的催化剂在"有水"条件下进行催化反应.这些研究成果对进一步扩展受限路易斯酸碱对（FLPs）化学的研究领域和应用前景提供了更多可能.本文以硅烷作为还原剂,在路易斯酸B（C₆F₅）₃催化下可在温和条件下实现醛与烷基羟胺类化合物的直接还原胺化反应,并且在还原过程中N-O键不会发生断裂,可中等至高产率地制备各种烷氧基取代的羟胺衍生物.对反应机理研究发现,在中性条件下苯甲醛与苄氧基羟胺的反应仅得到缩合中间产物肟醚,而在HCl或过量H₂O的参与下苯甲醛与苄氧基羟胺的直接还原胺化均可顺利进行;对反应机理的研究表明苄氧基羟胺会与路易斯酸硼烷在过量H₂O的参与下发生质子化,在硅烷的作用下转化成具有一定还原性的"硼氢化胺盐"活性中间体并进而促使中间产物肟醚的还原.对醛与羟胺的直接还原胺化反应研究表明,在"有水"条件下路易斯酸B（C₆F₅）₃不仅仅是一种"耐水"的催化剂,在某些反应中水可能直接影响着催化反应,尤其是对醛酮的直接还原胺化反应.因此,继续深入研究有"水"条件下路易斯酸硼烷参与的催化反应机理不仅对FLPs化学的发展至关重要,对其他相应催化体系的研究也具有重要的参考价值.     

“金属的电化学腐蚀”教学设计创新

以学科理解为基础,注重创设真实的教学情境,创新实验设计,使学生在探究暖贴发热原理和钢铁腐蚀原理的过程中获得金属电化学腐蚀的知识,拓展认知结构,学习科学方法,发展科学探究能力。     

Carbon nitride with encapsulated nickel for semi-hydrogenation of acetylene: pyridinic nitrogen is responsible for hydrogen dissociative adsorption

A new mechanism of catalyst has been demonstrated in this article. With the interaction between carbon nitride (CN) and encapsulated nickel, the CN in the catalyst has been endowed with new active sites for the adsorption and activation of hydrogen while nickel itself is physically isolated from the contact with reactive molecules. For the selective hydrogenation of acetylene in large amount of ethylene, the catalyst shows excellent ethylene selectivity than the nickel catalyst itself, which is almost totally unselective. Meanwhile, the CN itself is inactive for the reaction. The results of characterization demonstrate that pyridinic nitrogen doped in the carbon matrix should be the active sites for hydrogen dissociative adsorption. The theoretical calculations further confirm the results and provide with the detail in the electron transfer between nickel and CN in the catalyst. The current results supply a new concept for design of high performance catalyst.     

Controlling Proton and Electron Transfer Rates to Enhance the Activity of an Oxygen Reduction Electrocatalyst

An electrochemical approach is developed that allows for the control of both proton and electron transfer rates in the O₂ reduction reaction (ORR). A dinuclear Cu ORR catalyst was prepared that can be covalently attached to thiol‐based self‐assembled monolayers (SAMs) on Au electrodes using azide–alkyne click chemistry. Using this architecture, the electron transfer rate to the catalyst is modulated by changing the length of the SAM, and the proton transfer rate to the catalyst is controlled with an appended lipid membrane modified with proton carriers. By tuning the relative rates of proton and electron transfer, the current density of the lipid‐covered catalyst is enhanced without altering its core molecular structure. This electrochemical platform will help identify optimal thermodynamic and kinetic parameters for ORR catalysts and catalysts of other reactions that involve the transfer of both protons and electrons.     

Enantioselective Construction of Silicon‐Stereogenic Silanes by Scandium‐Catalyzed Intermolecular Alkene Hydrosilylation

The catalytic asymmetric construction of silicon‐stereogenic silanes is of great interest and significance, but has met with only limited success to date. We herein report the enantioselective hydrosilylation of alkenes with dihydrosilanes by a chiral half‐sandwich scandium catalyst, which constitutes an efficient and general route for the synthesis of a wide range of enantioenriched silicon‐stereogenic silanes from easily accessible starting materials. This reaction features a broad substrate scope, high yields, and high enantioselectivity. Some of the chiral tertiary silane products were also converted into valuable derivatives, such as chiral silanol, quaternary silane, and benzosilole compounds.     

1α-羟基去氢表雄酮的合成方法改进

以1,4-雄烯二酮为起始原料,经羰基保护、溴代消除、氧化、不完全氢化及脱保护等6步反应,以29%的总收率合成1α-羟基去氢表雄酮。该方法具有经济、技术可行、安全环保等优点,为1α-羟基去氢表雄酮的规模化生产及维生素D类药物合成研究奠定理论基础。     

Solvent‐Dependent Asymmetric Synthesis of Alkynyl and Monofluoroalkenyl Isoindolinones by CpRhIII‐Catalyzed C−H Activation

The asymmetric synthesis of alkynyl and monofluoroalkenyl isoindolinones from N‐methoxy benzamides and α,α‐difluoromethylene alkynes is enabled by C?H activation with a chiral CpRh^III catalyst. Remarkably, product formation is solvent‐dependent; alkynyl isoindolinones are afforded in MeOH (up to 86 % yield, 99.6 % ee) whereas monofluoroalkenyl isoindolinones are generated in ⁱPrCN (up to 98:2 Z/E, 93 % yield, 86 % ee). Mechanistic studies revealed chiral allene and E‐configured alkenyl rhodium species as reaction intermediates. The latter is transformed into the corresponding Z‐configured monofluoroalkene upon protonation in the ⁱPrCN system and into an alkyne by an unusual anti β‐F elimination in the MeOH system. Notably, kinetic resolution processes occur in this reaction. Despite the moderate enantiocontrol for the formation of the chiral allene, the Z‐monofluoroalkenyl isoindolinones and alkynyl isoindolinones were obtained in good enantiopurities by one or two sequential kinetic resolution processes.