Highly stereoselective synthesis of (Z)-3-methoxy-1-methyleneisoindoles via DMAP catalyzed cyclization of methyl 2-alkynylbenzimidates

A DMAP (4-dimethylaminopyridine) catalyzed cyclization of methyl 2-alkynylbenzimidates has been developed, which affords 3-methoxy-1-methyleneisoindoles with excellent Z-stereoselectivity under mild and transition-metal-free conditions. The (Z)-3-methoxy-1-methyleneisoindole products can be converted to corresponding 3-amino-1-methyleneisoindoles, 3-methoxy-isoindoles, 3-methyleneisoindolinones and isoindolinones with high efficiency.     

Total synthesis of methyl protodioscin: a potent agent with antitumor activity

Methyl protodioscin (1), otherwise known as 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-d-glucopyranosyl]-26-O-[beta-D-glucopyranosyl]-22-methoxy-25(R)-furost-5-ene-3 beta,26-diol, has been synthesized for the first time from diosgenin through nine steps in an overall yield of 7.8%.     

A concise and diversity-oriented strategy for the synthesis of benzofurans and indoles via Ugi and Diels-Alder reactions

A one-pot synthesis of diverse benzofurans and indoles from readily available starting materials was achieved via the sequential Ugi four-component reaction, intramolecular Diels-Alder reaction, and oxidative aromatization.     

Cs-Fe-Co-Bi-Mn-Mo复合氧化物选择性催化氧化异丁烯

Mixed oxide catalyst Cs0.1 Fe2Co6BiMnMo12 Ox was prepared by the interprecipitation method, then the catalyst was calcined at different temperature. Selective oxidation of isobutene was carried out in a fixed-bed reactor. The results showed that the catalyst has high catalytic activity. Under the optimum reaction conditions ( n(-C4^= ) : n(O2) = 1:2-1:4, space velocity = 180h^-1, T = 360℃ ), the yield of methacmlein and methacrylic reached 80%, 8 %,respectively. The total yields of liquid products( methacrolein, methacrylic acid and acetic acid) reached about 90%.     

Real‐Time Probing of Nanowire Assembly Kinetics at the Air–Water Interface by In Situ Synchrotron X‐Ray Scattering

Although many assembly strategies have been used to successfully construct well‐aligned nanowire (NW) assemblies, the understanding of their assembly kinetics has remained elusive, which restricts the development of NW‐based device and circuit fabrication. Now a versatile strategy that combines interfacial assembly and synchrotron‐based grazing‐incidence small‐angle X‐ray scattering (GISAXS) is presented to track the assembly evolution of the NWs in real time. During the interface assembly process, the randomly dispersed NWs gradually aggregate to form small ordered NW‐blocks and finally are constructed into well‐defined NW monolayer driven by the conformation entropy. The NW assembly mechanism can be well revealed by the thermodynamic analysis and large‐scale molecular dynamics theoretical evaluation. These findings point to new opportunities for understanding NW assembly kinetics and manipulating NW assembled structures by bottom‐up strategy.     

Biofunctional magnetic nanoparticles as contrast agents for magnetic resonance imaging of pancreas cancer

We report on the fabrication and characterization of biofunctional magnetic nanoparticles as contrast agents for magnetic resonance imaging. The anti-cancer antigen 19-9 monoclonal antibody (a cancer-targeting antibody) was conjugated onto the magnetic contrast agents in an effort to detect pancreatic tumor. The structure, size, morphology and magnetic property of the biofunctional magnetic nanoparticles are characterized systematically by means of transmission electron microscopy and X-ray diffractometry. Furthermore, the interaction between the nanoparticles and pancreas cancers cells are investigated by atomic force microscope and transmission electron microscopy. Magnetic resonance imaging demonstrates that the conjugated nanoparticles can effectively target cancer cells both in vitro and in vivo, suggesting that they potentially can be used as contrast agents for magnetic resonance imaging of pancreas cancer.     

甲烷氧化偶联Ti-La-Li系多元氧化物催化剂的表面碱性和表面活性氧种

利用ＣＯ２－ＴＰＤ方法考察了Ｔｉ－Ｌａ－Ｌｉ系多元氧化物催化剂的表面碱性，实验发现：Ｃ２选择性与表面碱强度呈顺变关系，而ＣＨ４转化率与ＣＯ２的脱附峰面积呈顺变关系。同时，利用ＸＰＳ，Ｏ２－ＴＰＤ等方法对该体系催化剂的表面活性氧种进行了表征与研究。结果表明：催化剂的表面晶格氧与Ｃ２选择性有关，表面吸附氧与甲烷转化（包括偶联和深度氧化）有关。Ｏ２－ＴＰＤ实验发现催化剂的表面存在三种氧。α（１００℃≤ｔ     

Asymmetric Synthesis of a Fused Tricyclic Hydronaphthofuran Scaffold by Desymmetric [2+2+2] Cycloaddition

A rhodium(I)‐BINAP‐catalyzed highly enantioselective [2+2+2] cycloaddition of enynes with alkynes has been developed. Diverse fused tricyclic hydronaphthofuran scaffolds with three consecutive stereogenic centers were constructed in one step from easily available materials with excellent chemo‐, regio‐, diastereo‐, and enantioselectivity. Notable features of these reactions include 100 % atom economy, very broad scope, and mild reaction conditions.     

Pseudoscalar quarkonium exclusive decays to vector meson pair

The pseudoscalar quarkonia exclusive decays to light mesons still poses a challenge to the theoretical understanding of quarkonium properties in decay. In this work, we evaluate the processes of pseudoscalar heavy quarkonium decays into vector meson pairs, especially the helicity suppressed processes of ηb→J/ψJ/ψ and ηc→VV. In the framework of NRQCD, the branching fraction of Br[ηb→J/ψJ/ψ] are evaluated at the next-to-leading order of perturbative QCD; and within the light-cone distribution formalism, we calculate also the higher twist effects in these processes. Numerical results show that the higher twist terms contribute more than what from the NLO QCD corrections in the process of ηb→J/ψJ/ψ. It is found that the experimental results on ηc→VV are hard to be understood by merely the quark model and perturbative QCD calculation.     

MgB2超导薄膜的微波测量

报道了利用蓝宝石介质谐振器技术测量MgB2超导薄膜的微波表面电阻Rs、OK时的穿透深度λ(O)和超导能隙△(O)．λ(O)和△(O)的值是通过先测量样品穿透深度λ(T)的变化量△λ(T)，然后由BCS理论模型拟合△λ（T)的实验数据得到的．测试样品是利用化学气相沉积技术在MgO(111)基片上制备的c轴织构的MgB2超导薄膜，薄膜的超导转变温度和转变宽度分别为38K和0．1K．微波测试结果表明在10K，18GHz下MgB2薄膜的Rs约为100μΩ，可以和高质量的YBCO薄膜的Rs值相比拟；BCS理论拟合得到的MgB2超导薄膜的λ(0)=102nm，△(0)：1．13kTc．