Sc(OTf)3-catalyzed tandem (3+3)-annulation/lactonization of cyclopropanes with salicylaldehyde nitrones to access polycyclic 1,2-oxazines

A Sc(OTf)₃-catalyzed tandem (3 + 3)-annulation/lactonization of donor-acceptor cyclopropane 1,1-dieters with salicylaldehyde nitrones has been reported, affording a wide range of tetrahydrochromeno[4,3-c][1,2]oxazin-5(1H)-ones in moderate yields with excellent diastereoselectivities. Besides, the gram-scale reaction has also been explored to demonstrate the utility of this protocol. Moreover, the mechanism was investigated through control experiments, which show the reaction proceeds via a tandem (3 + 3)-annulation/lactonization reaction.     

Green synthesis of Fe3O4 nanoparticles for hyperthermia,magnetic resonance imaging and 5-fluorouracil carrier in potential colorectal cancer treatment

Research on Chemical Intermediates - Magnetite nanoparticles (Fe3O4 NPs) have received considerable attention in various biomedical applications due to their fascinating properties and multiple...     

A Targeted Nano Drug Delivery System of AS1411 Functionalized Graphene Oxide Based Composites

A novel method for the preparation of antitumor drug vehicles has been optimized. Biological materials of chitosan oligosaccharide (CO) and γ-polyglutamic acid (γ-PGA) have previously been employed as modifiers to covalently modify graphene oxide (GO), which in turn loaded doxorubicin (DOX) to obtain a nano drug delivery systems of graphene oxide based composites (GO-CO-γ-PGA-DOX). The system was not equipped with the ability of initiative targeting, thus resulting into toxicity and side effects on normal tissues or organs. In order to further improve the targeting property of the system, the nucleic acid aptamer NH₂-AS1411 (APT) of targeted nucleolin (C23) was used to conjugate on GO-CO-γ-PGA to yield the targeted nano drug delivery system APT-GO-CO-γ-PGA. The structure, composition, dispersion, particle size and morphology properties of the synthesized complex have been studied using multiple characterization methods. Drug loading and release profile data showed that APT-GO-CO-γ-PGA is provided with high drug loading capacity and is capable of controlled and sustained release of DOX. Cell experimental results indicated that since C23 was overexpressed on the surface of Hela cells but not on the surface of Beas-2B cells, APT-GO-CO-γ-PGA-DOX can target Hela cells and make increase toxicity to Hela cells than Beas-2B cells, and the IC₅₀ value of APT-GO-CO-γ-PGA-DOX was 3.23±0.04 μg/mL. All results proved that APT-GO-CO-γ-PGA can deliver antitumor drugs in a targeted manner, and achieve the effect of reducing poison, which indicated that the targeted carrier exhibits a broad application prospect in the field of biomedicine.     

透射式阴极X光二极管初步研究

基于透射式阴极发射模型和平响应XRD原理,设计了透射式阴极,并制作550 nm CH+50 nm Au的阴极,并在神光Ⅲ原型装置上开展了初步验证实验。首先利用反射式XRD施加负偏压的实验开展直穿光影响评估,施加偏压为-1500 V时,没有观测到探测信号,表明直穿光产生光电子得到了有效抑制。利用原型主激光与第九路激光打靶实验,施加负偏压的透射式XRD获得探测信号显示第二个峰值信号延后第一个信号3.01 ns,该结果与第九路激光延迟时间一致,时间分辨能力满足实验要求。     

氢化铝锂新合成方法的研究

在略高溫度下,通过氯化锂和金属钠在氫气氛中的反应,得到了氢化锂和氯化钠的混合物。用通常的Schlesinger法将得到的混合物用于合成氢化铝锂。反应的副产物是氯化锂和氯化钠的混合物,可用不同方法将其分离,所得氯化锂用于再循环。     

经颅磁刺激感应外电场作用下最小神经元模型放电起始动态机理分析

经颅磁刺激(TMS)是一种采用电磁线圈在大脑指定区域产生磁场的刺激方式. TMS的治疗原理是通过电磁感应产生作用于神经元的外加电场进而影响神经元编码. 然而目前TMS感应外电场改变神经元编码的内在机理尚不清楚.研究表明, 神经元编码由神经元的放电起始动态机理决定. 本文建立了TMS感应外电场作用下的最小神经元模型, 采用相平面分析和分岔分析方法, 研究了外电场作用下神经元放电起始动态的动力学机理, 并从阈下电位的不同动力学特性离子电流竞争角度揭示了TMS感应外电 场作用下神经元放电起始动态的生理学机理.     

Chloropupukeanolides C-E: cytotoxic pupukeanane chlorides with a spiroketal skeleton from Pestalotiopsis fici

Chloropupukeanolides C–E ( 8 – 10 ), three highly functionalized secondary metabolites featuring a novel spiroketal skeleton derived from the chlorinated tricyclo‐[4.3.1.0^{3, 7}]‐decane (pupukeanane) and the 2,6‐dihydroxy‐4‐methylbenzoic acid moieties, were isolated from the scale‐up fermentation extract of the plant endophytic fungus Pestalotiopsis fici. The constitutions of compounds 8 – 10 were elucidated primarily by NMR experiments. Their relative configurations were deduced by analogy to metabolites 4 – 6 , which were previously isolated from the same fungus. The absolute configuration of 8 was assigned by X‐ray crystallography and those of 9 and 10 by quantum‐chemical CD calculations. Biogenetically, chloropupukeanolides C–E ( 8 – 10 ) are presumably derived from the same oxidation‐induced Diels–Alder reaction pathway as compounds 1 and 4 – 7 , via the putative biosynthetic precursors 2 and 3 . The opposite configurations of the complete “Southern parts” of 8 and 9 suggests that this Diels–Alder reaction is stereochemically not very selective. Compounds 8 – 10 showed significant cytotoxicity against a small panel of human tumor cell lines and weak activities against the pathogens of tropical diseases.     

Luminescent Palladium(II) Complexes with π‐Extended Cyclometalated [RC^N^NR′] and Pentafluorophenylacetylide Ligands: Spectroscopic,Photophysical, and Photochemical Properties

A series of cyclometalated Pd^II complexes that contain π‐extended R? C^N^N? R′ (R? C^N^N? R′=3‐(6′‐aryl‐2′‐pyridinyl)isoquinoline) and chloride/pentafluorophenylacetylide ligands have been synthesized and their photophysical and photochemical properties examined. The complexes with the chloride ligand are emissive only in the solid state and in glassy solutions at 77 K, whereas the ones with the pentafluorophenylacetylide ligand show phosphorescence in the solid state (λ_max=584–632 nm) and in solution (λ_max=533–602 nm) at room temperature. Some of the complexes with the pentafluorophenylacetylide ligand show emission with λ_max at 585–602 nm upon an increase in the complex concentration in solutions. These Pd^II complexes can act as photosensitizers for the light‐induced aerobic oxidation of amines. In the presence of 0.1 mol % Pd^II complex, secondary amines can be oxidized to the corresponding imines with substrate conversions and product yields up to 100 and 99 %, respectively. In the presence of 0.15 mol % Pd^II complex, the oxidative cyanation of tertiary amines could be performed with product yields up to 91 %. The Pd^II complexes have also been used to sensitize photochemical hydrogen production with a three‐component system that comprises the Pd^II complex, [Co(dmgH)₂(py)Cl] (dmgH=dimethylglyoxime; py=pyridine), and triethanolamine, and a maximum turnover of hydrogen production of 175 in 4 h was achieved. The excited‐state electron‐transfer properties of the Pd^II complexes have been examined.     

Ruthenium–Porphyrin‐Catalyzed Diastereoselective Intramolecular Alkyl Carbene Insertion into C?H Bonds of Alkyl Diazomethanes Generated In Situ from N‐Tosylhydrazones

With a ruthenium–porphyrin catalyst, alkyl diazomethanes generated in situ from N‐tosylhydrazones efficiently underwent intramolecular C(sp³) H insertion of an alkyl carbene to give substituted tetrahydrofurans and pyrrolidines in up to 99 % yield and with up to 99:1 cis selectivity. The reaction displays good tolerance of many functionalities, and the procedure is simple without the need for slow addition with a syringe pump. From a synthetic point of view, the C H insertion of N‐tosylhydrazones can be viewed as reductive coupling between a CO bond and a C H bond to form a new C C bond, since N‐tosylhydrazones can be readily prepared from carbonyl compounds. This reaction was successfully applied in a concise synthesis of (±)‐pseudoheliotridane.