Three New Diterpenoids from Euphorbia sororia L.

Three new diterpenoids with jatrophane‐type skeleton, sororianolides A–C ( 1 – 3 , resp.), were isolated from Euphorbia sororia. The identification and structure elucidation of these compounds were based on 1D‐ and 2D‐NMR‐spectral data analysis. It was the first time to isolate diterpenoids in this species.     

A synthesis of carbasugar-sugar pseudodisaccharides via a cycloaddition-cycloreversion reaction of 2H-pyran-2-ones

Cycloaddition of 3-carbomethoxy-2H-pyran-2-one to a vinylated sugar followed by the loss of bridging CO(2) from the cycloadduct affords a cyclohexadiene which can be manipulated to a carbasugar-sugar pseudodisaccharide.     

Synthesis and QSAR studies on 1-[(5-substituted-1,3,4-thiadiazol-2-yl)methyl]-1H-1,2,4-triazole as antifungal agents

A series of 1-[(1,3,4-thiadiazol-2-yl)methyl]-1H-1,2,4-triazole derivatives were prepared and evaluated for their antifungal activities. The chemical structures of these compounds were determined by means of elemental analyses, ¹H NMR, and X-ray crystallography. Quantitative structure–activity relationship (QSAR) studies were performed on these compounds using physicochemical parameters as independent parameters and antifungal activity as a dependent parameter, where antifungal activity correlated best (r > 0.9) with hydrophobic parameters (π) and indicator (H). Moreover, the results are interpreted on the basis of a multiple regression model. The model has been internally and externally validated. Furthermore, the domain of applicability which indicates the area of reliable predictions is defined.     

Quasinormal and Hyponormal Weighted Composition Operators on $$H^2$$ and $$A^2_{\alpha }$$Aα2 with Linear Fractional Compositional Symbol

In this paper, we study quasinormal and hyponormal composition operators \(W_{\psi ,\varphi }\)  with linear fractional compositional symbol \(\varphi \) on the Hardy and weighted Bergman spaces. We characterize the quasinormal composition operators induced on \(H^{2}\) and \(A_{\alpha }^{2}\) by these maps and many such weighted composition operators, showing that they are necessarily normal in all known cases. We eliminate several possibilities for hyponormal weighted composition operators but also give new examples of hyponormal weighted composition operators on \(H^2\) which are not quasinormal.     

SEPARATION OF THE MINOR FLAVONOLS FROM FLOS GOSSYPII BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY

An effective high-speed countercurrent chromatography (HSCCC) method was established for further separation and purification of four minor flavonols in addition to five major flavonols which were reported by our previous study from extracts of Flos Gossypii. HSCCC was performed with three two-phase solvent systems composed of n-hexane-ethyl acetate-methanol-water (7.5:15:6:7, v/v), (2.5:15:2:7, v/v) and (0:1:0:1, v/v). The separation was repeated 3 times, and 3.8 mg of 8-methoxyl-kaempferol-7-O-β-D-rhamnoside (HPLC purity 98.27%), 6.7 mg of astragalin (HPLC purity 94.18%), 3.3 mg of 4'-methoxyl-quercetin-7-O-β-D-glucoside (HPLC purity 94.30%) and 8.2 mg of hyperoside (HPLC purity 93.48%) were separated from 150 mg of the crude sample. The chemical structures of the flavonols were confirmed by MS, (1)H NMR and (13)C NMR. Meanwhile, the results indicated that the target compound with smaller K value (<0.5) can be separated by increasing column length of HSCCC. And four separation rules of flavonols according to the present study and references were summarized, which can be used as a useful guide for separation of flavonols by HSCCC.     

On the latest starting times and criticality of activities in a network with imprecise durations

This paper deals with problems of computing possible values of latest starting times and determining types of criticality for all activities in a network with interval or fuzzy activity durations. Although the problem of computing the latest starting times has been solved, a novel polynomial algorithm which is easy to understand and improves complexity is proposed.     

Preconcentration of copper with dithizone-naphthalene for subsequent determination by atomic absorption spectrometry

A simple and convenient method for the separation and preconcentration of copper from aqueous samples has been developed. The procedure is based on the chemical sorption of copper(II) onto a column packed with immobilized dithizone on microcrystalline naphthalene. The trapped copper is eluted with 10 mL of 4 M nitric acid and determined by flame atomic absorption spectrometry. A preconcentration factor of 200 was obtained for a volume of 2 L. The relative standard deviation for the determination of 5 and 10 μg/L copper was 2.2 and 1.7%, respectively. The procedure was successfully applied to the determination of copper in water and alloy samples. The accuracy was assessed through the analysis of certified reference materials or recovery experiments. The text was submitted by the authors in English.     

The Efficiency of a Microcolumn of Rice Bran for On‐line Trace Enrichment in FI‐AAS,a Highly Selective System for On‐line Preconcentration and Determination of Copper

A flow injection flame atomic absorption spectrometry system incorporating a microcolumn of rice bran was designed, and its capability for on‐line trace enrichment of copper, cadmium and lead was studied. Analytes were deposited on the microcolumn by processing a standard or solution of analytes on the column. Injection of 250 μL of nitric acid (1 mol/L) then served to elute the retained species to FAAS. The procedure was successfully applied for determination of copper in tap water, well water and multivitamin tablets. The accuracy was assessed through recovery experiments and independent analysis by furnace‐AAS. A sample volume of 20 mL of copper resulted in a preconcentration factor of 96; precision value at the 20 μg/L was 4.1%.     

低温制备高纯度番茄红素异构体及其在食用油中的异构化及降解研究

该文通过将低温C18色谱柱和C30色谱柱组合构建了可用于番茄红素异构体纯化的正交分离方法.研究表明,当色谱柱温低于-20 ℃时,普通C18色谱柱对番茄红素异构体的分离度得到大幅增加.研究了番茄红素的溶解度与分离度之间的关系,并通过该正交方法最终制备了7种纯度均高于97％的番茄红素异构体.相比于单独使用C18柱或C30柱...     

A quantitative structure-activity relationship study of antifungal analogues of 3,4-substituted 5-((1H-1, 2, 4-triazol-1-yl)methyl)-4H-1,2,4-triazole

A series of 5-((1H-1, 2, 4-triazol-1-yl)methyl)-4H-1,2,4-triazole derivatives were prepared and evaluated for their antifungal activities. Quantitative structure–activity relationship studies were performed on these compounds using physicochemical parameters as independent parameters and antifungal activity as a dependent parameter, where antifungal activity correlated best (correlation coefficient r > 0.8) with physicochemical parameters (Hammett’s constants σ _p , F) and van der Waals volume V ₁. Results are interpreted on the basis of multiple regression and cross-validation methodology. Furthermore, the domain of applicability which indicates the area of reliable predictions is defined. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Chemical structures of A1–26 and A39; synthetic procedures; synthesis schemes; mps, yields, ¹H NMR; elemental analyses of compounds and single crystal X-ray diffraction of compounds.