Facile Synthesis of Chiral Spirooxindole‐Based Isotetronic Acids and 5‐1H‐Pyrrol‐2‐ones through Cascade Reactions with Bifunctional Organocatalysts

Unprecedented organocatalyzed asymmetric cascade reactions have been developed for the facile synthesis of chiral spirooxindole‐based isotetronic acids and 5‐1H‐pyrrol‐2‐ones.The asymmetric 1,2‐addition reactions of α‐ketoesters to isatins and imines by using an acid–base bifunctional 6′‐OH cinchona alkaloid catalyst, followed by cyclization and enolization of the resulting adducts, gave chiral spiroisotetronic acids and 5‐1H‐pyrrol‐2‐ones, respectively, in excellent optical purities (up to 98 % ee). FT‐IR analysis supported the existence of hydrogen‐bonding interaction between the 6′‐OH group of the cinchona catalyst and an isatin carbonyl group, an interaction that might be crucial for catalyst activity and stereocontrol.     

Synthesis,Thermal Behavior,and Dehydrogenation Kinetics Study of Lithiated Ethylenediamine

The lithiation of ethylenediamine by LiH is a stepwise process to form the partially lithiated intermediates LiN(H)CH₂CH₂NH₂ and [LiN(H)CH₂CH₂NH₂][LiN(H)CH₂CH₂N(H)Li]₂ prior to the formation of dilithiated ethylenediamine LiN(H)CH₂CH₂N(H)Li. A reversible phase transformation between the partial and dilithiated species was observed. One dimensional {Li_nN_n} ladders and three‐dimensional network structures were found in the crystal structures of LiN(H)CH₂CH₂NH₂ and LiN(H)CH₂CH₂N(H)Li, respectively. LiN(H)CH₂CH₂N(H)Li undergoes dehydrogenation with an activation energy of 181±8 kJ mol^?1, whereas the partially lithiated ethylenediamine compounds were polymerized and released ammonia at elevated temperatures. The dynamical dehydrogenation mechanism of the dilithiated ethylenediamine compounds was investigated by using the Johnson‐Mehl‐Avrami equation.     

A new fluorescent quenching method for the determination of phosphoproteins by using calconcarboxylic acid

A fluorescent quenching detection method for phosphoproteins in SDS‐PAGE by using calconcarboxylic acid (CCA) was described. In this method, the fluorescence intensity of CCA was greatly increased with the presence of Al³⁺ in the gel background, while in zones where phosphoproteins are located this intensity was absent because of fluorescence quenching phenomenon through the formation of CCA‐Al³⁺‐phosphoprotein appended complex. Approximately 4–8 ng of phosphoproteins can be selectively detected within 1 h (1D SDS‐PAGE), which is similar to that of the most commonly used Pro‐Q Diamond stain. The specificity of this novel technique for phosphoproteins was confirmed by dephosphorylation, Western blot, and LC‐MS/MS analysis, respectively. Furthermore, to better understand the newly developed method, the detection mechanism of CCA stain was explored by fluorescent spectrometry. According to the results, it is believed that CCA stain may provide a new choice for selective, economical, MS compatible, and convenient visualization of gel‐separated phosphoproteins.     

Novel and Efficient Synthesis of DHPMs Catalyzed by di‐DACH‐Pyridylamide Ligands

Di‐DACH‐pyridylamide ligands, symmetrical bridged bis‐Schiff base, and spiro pyrrolizines as catalysts in the synthesis of dihydropyrimidinethiones (DHPMs) using the Biginelli reaction is first reported. This new protocol has the advantages of environmental friendliness, short reaction time, excellent yields, and simple post‐treatment procedure. A series of DHPMs were obtained in high yields (up to 98%) in only 6 h. Moreover, based on the optimized condition, a novel Biginelli‐like reaction was first developed.     

Controlled release of doxorubicin from electrospun MWCNTs/PLGA hybrid nanofibers

In this study, multiwalled carbon nanotubes (MWCNTs) were used to encapsulate a model anticancer drug, doxorubicin (Dox). Then, the drug-loaded MWCNTs (Dox/MWCNTs) with an optimized drug encapsulation percentage were mixed with poly(lactide-co-glycolide) (PLGA) polymer solution for subsequent electrospinning to form drug-loaded composite nanofibrous mats. The structure, morphology, and mechanical properties of the formed electrospun Dox/PLGA, MWCNTs/PLGA, and Dox/MWCNTs/PLGA composite nanofibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and tensile testing. In vitro viability assay and SEM morphology observation of mouse fibroblast cells cultured onto the MWCNTs/PLGA fibrous scaffolds demonstrate that the developed MWCNTs/PLGA composite nanofibers are cytocompatible. The incorporation of Dox-loaded MWCNTs within the PLGA nanofibers is able to improve the mechanical durability and maintain the three-dimensional structure of the nanofibrous mats. More importantly, our results indicate that this double-container drug delivery system (both PLGA polymer and MWCNTs are drug carriers) is beneficial to avoid the burst release of the drug and able to release the antitumor drug Dox in a sustained manner for 42 days. The developed composite electrospun nanofibrous drug delivery system may be used as therapeutic scaffold materials for post-operative local chemotherapy.     

密度泛函理论下的分子总体电负性与调和平均电负性的关系

根据密度泛函理论定义的有效原子电负性，讨论了分子中总体电负性与调和平均电负性之间的关系，得到了调和平均电负性非常接近于总体电负性的结论，同时，说明了两者相似的原因，并对一系列分子给出了它们的数值比较．     

甲烷在二元碱土金属复合体系催化剂上的氧化偶联

碱土金属氧化物或碳酸盐为多种类型甲烷氧化偶联制取C_2烃催化剂的重要组分之一.有关纯碱土金属氧化物及含氧酸盐的研究表明,这类化合物具有较强的表面碱性及高温P型半导性而对活化甲烷生成C_2烃有较高活性,关于不同碱土金属化合物之间混合形成的二元碱土金属复合体系催化剂的报导仍不多见,Aika等人曾报导用BaO与CaO或MgO混合的催化剂上在1073K时可以获得61.1%C_2烃选择性和14.2%的C_2烃收率,但BaO易在反应条件下与水反应生成Ba(OH)_2而腐蚀器壁,不利于长期操作.本文报导了一系列不同碱土金属化合物之间形成的二元碱土复合体系催化剂上甲烷氧化偶联的反应结果.结果表明,这类催化剂由于其结构稳定、活性好而值得进一步研究.     

Formation of polymeric toroidal-spiral particles

Compared to spherical matrices, particles with well-defined internal structure provide large surface to volume ratio and predictable release kinetics for the encapsulated payloads. We describe self-assembly of polymeric particles, whereby competitive kinetics of viscous sedimentation, diffusion, and cross-linking yield a controllable toroidal-spiral (T-S) structure. Precursor polymeric droplets are splashed through the surface of a less dense, miscible solution, after which viscous forces entrain the surrounding bulk solution into the sedimenting polymer drop to form T-S channels. The intricate structure forms because low interfacial tension between the two miscible solutions is dominated by viscous forces. The biocompatible polymer, poly(ethylene glycol) diacrylate (PEG-DA), is used to demonstrate the solidification of the T-S shapes at various configurational stages by UV-triggered cross-linking. The dimensions of the channels are controlled by Weber number during impact on the surface, and Reynolds number and viscosity ratio during subsequent sedimentation. We anticipate applications of the T-S particle in drug delivery, wherein diffusion through these T-S channels and the polymer matrix would offer parallel release pathways for molecules of different sizes. Polyphosphate, as a model macromolecule, is entrained in T-S particles during their formation. The in vitro release kinetics of polyphosphate from the T-S particles with various channel length and width is reported. In addition, self-assembly of T-S particles occurs in a single step under benign conditions for delicate macromolecules, and appears conducive to scaleup.     

Solvation forces between silica bodies in supercritical carbon dioxide

We report Monte Carlo simulations of the solvation pressure between two planar surfaces, which represent the interface of spherical silica nanoparticles in supercritical carbon dioxide. Carbon dioxide (CO2) was modeled as an atomistic dumbbell or a spherical Lennard-Jones particle. The interaction between CO2 molecules and silica surfaces was characterized by the standard Steele potential with energetic heterogeneities representing the hydrogen bonds. The parameters for the solid-fluid interaction potentials were obtained by fitting our simulations to the experimental isotherms of CO2 sorption on mesoporous siliceous materials. We studied the dependence of the solvation force on the distance between planar silica surfaces at T = 318 K, at equilibrium bulk pressures p(bulk) ranging from 69 to 200 atm. At 69 atm, we observed a long-range attraction between the two surfaces, and it vanished when the pressure was increased to 102 and then 200 atm. The results obtained with different fluid models were consistent with each other. According to our observations, energetic heterogeneities of the surface have negligible influence on the solvation pressure. Using the Derjaguin approximation, we calculated the solvation forces between spherical silica nanoparticles in supercritical CO2 from the solvation pressures between the planar surfaces.     

Automated hollow fiber-protected dynamic liquid-phase microextraction of pesticides for gas chromatography-mass spectrometric analysis

Dynamic liquid-phase microextraction (LPME) controlled by a programmable syringe pump was evaluated for extracting pesticides in water prior to GC-MS analysis. A conventional microsyringe with a 1.3-cm length of hollow fiber attached to its needle was connected to a syringe pump to perform the extraction. The microsyringe was used as both the microextraction device as well as the sample introduction device for GC-MS analysis. The attached hollow fiber served as the "holder" and protector" of 3 microl of organic solvent. The solvent was repeatedly withdrawn into and discharged from the hollow fiber by the syringe pump. Pesticides were extracted from 4-ml water samples into the organic solvent impregnated in the hollow fiber. The effects of organic solvents, plunger movement pattern, agitation and extraction time were investigated. Good repeatabilities of extraction performance were obtained, with the RSD values ranging from 3.0% (alachlor) to 9.8% (4-chlorophenol) for the 14 pesticides; most RSD values were under 5.0%. The method provided a 490-fold preconcentration of the target pesticides. The limits of detection were in the range of 0.01-5.1 microg/l (S/N = 3) in the GC-MS selected ion monitoring mode. In addition, sample clean-up was achieved during LPME because of the selectivity of the hollow fiber, which prevented undesirable large molecules from being extracted. A slurry sample (mixture of 40 mg soil/ml of water) containing seven pesticides was extracted using this method which also gave good linearity and precision (most RSDs <7.0%, n = 3).