Transition from π Radicals to σ Radicals: Substituent‐Tuned Cyclization of Hydrazonyl Radicals

Hydrazonyl radicals are known for their π‐electronic structures; however, their σ‐electronic structures have not been reported as yet. Herein, we show that readily accessible β,γ‐ and γ,δ‐unsaturated N‐trichloroacetyl and N‐trifluoroacetyl hydrazones can be conveniently converted into hydrazonyl σ radicals, which subsequently undergo 5‐exo‐trig radical cyclization at the N¹ or N² atom to form pyrazolines and azomethine imines, respectively.     

Tailoring 3,3′‐Dihydroxyisorenieratene to Hydroxystilbene: Finding a Resveratrol Analogue with Increased Antiproliferation Activity and Cell Selectivity

Four novel compounds were designed by “tailoring” 3,3′‐dihydroxyisorenieratene (a natural carotenoid) based on an isoprene unit retention truncation strategy. Among them, the smallest molecule 1 (2,3,6,2′,3′,6′‐hexamethyl‐4,4′‐dihydroxy‐trans‐stilbene) was concisely synthesized in a one‐pot Stille–Heck tandem sequence, and surfaced as a promising lead molecule in terms of its selective antiproliferative activity mediated by blocking the NCI‐H460 cell cycle in G1 phase. Additionally, theoretical calculations and cell uptake experiments indicate that the unique polymethylation pattern of compound 1 significantly induces a conformational change shift out of planarity and increases its cell uptake and metabolic stability. The observation should be helpful to rationally design resveratrol‐inspired antiproliferative agents.     

Enantioselective Iron‐Catalyzed Intramolecular Cyclopropanation Reactions

An iron‐catalyzed asymmetric intramolecular cyclopropanation was realized in high yields and excellent enantioselectivity (up to 97 % ee) by using the iron complexes of chiral spiro‐bisoxazoline ligands as catalysts. The superiority of iron catalysts exhibited in this reaction demonstrated the potential abilities of this sustainable metal in asymmetric carbenoid transformation reactions.     

哈茨木霉CGMCC 2979生物转化栀子中的京尼平苷制备京尼平

采用微生物直接转化药材的方法,将栀子中的京尼平苷转化为京尼平,无需糖苷酶和京尼平苷的制备. 在培养温度为30 ℃,pH 6.1以及栀子载量为80 g/L的条件下,48 h京尼平苷的转化率为97.8%. 转化后的京尼平通过XAD-16N大孔树脂偶联硅胶层析的方法,制备得到纯度大于95%的京尼平,收率为62.3%. 在催化、转化机制研究中,从哈茨木霉CGMCC2979的发酵液中分离得到了分子量为74.4 kDa的京尼平苷β-葡萄糖苷酶,该酶最优催化条件为50 ℃和pH 4.0-5.0. K_m和V_max分别为3.6 mmol/L和775 μmol/h/mg蛋白. 本文提供了一种简便、高效制备京尼平的新方法.     

Synthesis of star-shaped polyhedral oligomeric silsesquioxane (POSS) fluorinated acrylates for hydrophobic honeycomb porous film application

Two different eight-arm star-shaped polyhedral oligomeric silsesquioxane (POSS) fluorinated acrylates were synthesized through atom transfer radical polymerization (ATRP) and applied for hydrophobic honeycomb-patterned porous films through the breath figure (BF) method. The structure of polymers was characterized by Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC), and surface analysis was featured by X-ray photoelectron spectroscopy (XPS). Depending on the influences of polymer architectures, solvents utilized, and solution concentrations, honeycomb-patterned porous films were obtained. It could be found that the introduction of fluorine components was a favorable condition for BF formation and chloroform (CHCl₃) utilized as solvent with an appropriate concentration of 30 mg/mL was the best condition for these hydrophobic honeycomb-patterned porous films. Meanwhile, the obtained honeycomb films could be retained after long-time preservation in an acid-base condition, which shows a great potential in filtration, cell culture, tissue engineering, and marine antifouling applications.     

磷脂膜的相行为对氧化石墨烯与磷脂膜相互作用的影响

通过使用不同相变温度的磷脂分子并调节二者的比例构筑了不同相态的磷脂膜, 并利用表面增强红外光谱和激光共聚焦显微镜研究了磷脂膜的相行为对氧化石墨烯和磷脂膜相互作用的影响. 结果表明, 氧化石墨烯对磷脂膜中磷脂分子的抽提作用具有显著的相态选择性, 其选择性地抽提流动相的磷脂分子; 氧化石墨烯对流动相磷脂的抽提作用受到膜中凝胶相磷脂存在比例的影响, 只有在流动相磷脂分子占磷脂膜中磷脂分子的绝大部分时才能够发生抽提作用, 且只有流动相的磷脂分子被抽提.     

高效液相色谱法结合一测多评法对隔山消发酵前后3种苯乙酮类化合物含量变化的分析

采用高效液相色谱法结合一测多评法测定了隔山消发酵前后2,4-二羟基苯乙酮、2,5-二羟基苯乙酮和白首乌二苯酮等3种苯乙酮类化合物的含量。分别制备发酵前后的隔山消样品溶液,色谱分析中采用Thermo C18色谱柱作为固定相,用不同比例的水(A)、乙腈(B)和甲醇(C)的混合液作为流动相进行梯度洗脱,达到上述3种组分的良好分离。采用二极管阵列检测器在相同的检测波长(265nm处)分别测定3种组分的峰面积。分别用一测多评法(QAMS)和外标法计算所测定组分的含量,结果表明两种计算方法所得结果相似性极高,据此认为在隔山消发酵前后的样品溶液中各组分的质量评价中采用QAMS是可行的。按上述方法分析了同一批隔山消样品12份,取其中6份经发酵处理,对所得结果的平均值进行了比较,未经发酵的样品溶液中2,4-二羟基苯乙酮的质量分数为0.208mg·g^-1、2,5-二羟基苯乙酮的质量分数为0.152mg·g^-1,与经发酵的样品溶液中的质量分数(2,4-二羟基苯乙酮的质量分数为0.235mg·g^-1、2,5-二羟基苯乙酮的质量分数为0.180mg·g^-1)相比呈升高趋势,而白首乌二苯酮的质量分数由未经发酵样品溶液中的0.678mg·g^-1下降为发酵样品溶液中的0.543mg·g^-1。此外,研究结果还表明,不同含量的2,5-二羟基苯乙酮和白首乌二苯酮相对于2,4-二羟基苯乙酮(参照物)的相对校正因子和相对保留时间基本相同。     

Synthesis of Zinc Tetraaminophthalocyanine Functionalized Graphene Nanosheets as an Enhanced Material for Sensitive Electrochemical Determination of Uric Acid

A new electrochemical sensor material has been fabricated via the non‐covalent functionalization of reduced graphene oxide (rGO) and soluble tetramino zincphthalocyanines (ZnPc‐NH₂). Immobilization of uricase onto the synthesized nanohybrids can evidently improve the electrocatalytic activity and selectivity. The obtained composite membrane possesses a great enhancement of electron transfer rate and excellent synergistic electrocatalytic effect toward uric acid (UA) oxidation under the working potential at 0.620 V vs. Ag/AgCl with a scan rate of 0.125 V/s. The effects of the experimental parameters on the electrochemical oxidation responses of UA were investigated and optimized in detail. Under the optimized conditions, the peak currents were proportional to the UA concentration in a range from 0.5 to 100 μmol/L with detection limit of 0.15 μmol/L. Moreover, the developed sensor was applied for UA determination in human urine samples with high accuracy and satisfactory recovery, which is envisioned to have promising applications in monitoring UA in clinical research.     

Principles of Surface Potential Estimation in Mixed Electrolyte Solutions:Taking into Account Dielectric Saturation

The dielectric properties between in-particle/water interface and bulk solution are significantly different, which are ignored in the theories of surface potential estimation. The analytical expressions of surface potential considering the dielectric saturation were derived in mixed electrolytes based on the nonlinear Poisson-Boltzmann equation. The surface potentials calculated from the approximate analytical and exact numerical solutions agreed with each other for a wide range of surface charge densities and ion concentrations. The effects of dielectric saturation became important for surface charge densities larger than 0.30 C/m\begin{document}$ ^2 $\end{document}. The analytical models of surface potential in different mixed electrolytes were valid based on original Poisson-Boltzmann equation for surface charge densities smaller than 0.30 C/m\begin{document}$ ^2 $\end{document}. The analytical model of surface potential considering the dielectric saturation for low surface charge density can return to the result of classical Poisson-Boltzmann theory. The obtained surface potential in this study can correctly predict the adsorption selectivity between monovalent and bivalent counterions.