A study of the thermal decarboxylation of three perfluoropolyether salts

The thermal decarboxylation of three dicarboxylic perfluoropolyether potassium salts of relatively short chain length has been investigated and the products and kinetics of the main reactions have been defined. From the rate constants and Arrhenius parameters data, the second decarboxylation appears to be quantitatively rather close to the first.     

Stevia rebaudiana targeting α-amylase: An in-vitro and in-silico mechanistic study

Diabetes mellitus (DM) is the fastest growing metabolic disorder in the world. Recently, more attention is paid to the study of natural products due to side effects of synthetic drugs. Stevia rebaudiana (Bertoni) is considered an encouraging starting point for the antidiabetic lead development. In the present study, the in vitro α-amylase inhibitory activity of the extracts of S. rebaudiana is investigated. In order to understand the molecular mechanism and future pharmacophore development, in silico study of secondary metabolites isolated from S. rebaudiana was carried out. Results indicated that water extract shows highest α-amylase inhibitory activity as compared to other extracts. Moreover, compound 20 (rebaudioside A) which has been previously reported and isolated from water extract showed the impressive binding profile with α-amylase. Therefore, our study suggests that S. rebaudiana could be used in the development of therapeutic drugs for the treatment of diabetes.     

Isolation and antiproliferative activity of triterpenoids and fatty acids from the leaves and stem of Turraea vogelii Hook. f. ex benth

Chloroform extract from the leaves of Turraea vogelii Hook f. ex Benth demonstrated cytotoxic activity against a chronic myelogenous leukemia cell, K-562 with IC₅₀ of 14.27 μg/mL, while chloroform, ethyl acetate and methanol extracts from the stem of the plant inhibited K-562 cells growth with IC₅₀ of 19.50, 24.10 and 85.40 μg/mL respectively. Bioactive chloroform extract of Turraea vogelii leaves affords two triterpenoids: oleana-12,15,20-trien-3β-ol (1), and oleana-11,13-dien-3β,16α,28-triol (2), with six fatty esters, ethyl hexaeicos-5-enoate (3), 3-hydroxy-1,2,3-propanetriyltris(tetadecanoate) (4), 1,2,3-propanetriyl(7Z,7′Z,7′′Z)tris(-7-hexadecenoate) (5), 1,2,3-propanetriyl(5Z,5′Z,5′′Z)tris(-5-hexadecenoate) (6), 1,2,3-propanetriyltris(octadecanoate) (7), and 2β-hydroxymethyl tetraeicosanoate (8). Tetradecane (9), four fatty acids: hexadecanoic acid (10), tetradecanoic acid (11), (Z)-9-eicosenoic acid (12), and ethyl tetradec-7-enoate (13) were isolated from chloroform extract of Turraea vogelii stem. 1,2,3-propanetriyltris(heptadecanoate) (14), (Z)-9-octadecenoic acid (15) and (Z)-7-tetradecenoic acid (16) were isolated from ethyl acetate extract while (Z)-5-pentadecenoic acid (17) was obtained from methanol extract of the plant stem. Compounds 1, 2, 5, 6, 11, 12, 15, 16 and 17 exhibited pronounced antiproliferative activity against K-562 cell lines.     

New catalytic effect of thiourea on the oxidative cyanation of N-aryltetrahydroisoquinolines

Thiourea itself has been introduced as a mild and efficient organocatalyst for the oxidative α -cyanation of N-aryltetrahydroisoquinolines (THIQs) with trimethylsilyl cyanide (TMSCN), giving the corresponding products in good to excellent yields. Experimental investigations demonstrated that thiourea acts as a radical initiator by abstracting hydroxyl radical (OH) from tert-butyl hydroperoxide (TBHP) directly instead of non-covalent hydrogen bondings (H-bondings) activation. The use of thiourea as a radical initiator offers a new avenue for innovative chemical transformations in organocatalyzed radical chemistry.     

α-Cu_2Se精细结构的球差校正扫描透射电镜表征

目前学界对Cu_2Se低温α相的结构仍未认识清楚,而解决这一问题对理解Cu_2Se在相变过程中热电性能提升等特性具有重要意义。本文首次报道了由球差校正扫描透射电镜(STEM)拍摄到的沿■带轴的原子级分辨率高角环形暗场(HAADF)像,揭示了由Se原子以多种形式有序起伏产生的复杂结构。结合电子衍射图谱,分析了包含不同层数、通过相互组合构成α-Cu_2Se晶体的多种结构变体。使用QSTEM软件对构建的结构变体进行高分辨图像模拟,得到了与实验对应的HAADF像。该工作为更全面地理解α-Cu_2Se的结构提供了新的重要信息。     

Recent synthetic methodologies for pyrazolo[1,5-a]pyrimidine

The development of new synthetic routes towards pyrazolo[1,5-a]pyrimidines for their biological and medicinal exploration is an attractive area for researchers. This review focuses on various synthetic routes developed in the last decade for the synthesis of differently substituted pyrazolo[1,5-a]pyrimidines by a broad range of organic reactions by means of 5-aminopyrazole as a precursor.     

无溶剂条件下α-羟基磷酸酯的合成

在无溶剂条件下,以碳酸钾做催化剂,芳香醛与亚磷酸酯在室温下通过研磨,合成了一系列磷酸酯类化合物.该反应条件温和,操作简单,时间短,对环境友好,是一种绿色的合成方法.产物结构经IR,MS,1HNMR等方法表征.     

pePC-SAFT: Modeling of polyelectrolyte systems: 1. Vapor–liquid equilibria

A molecular thermodynamic model for polyelectrolyte systems—called pePC-SAFT—is proposed. The effect of charged monomers within the polyelectrolyte chain is explicitly taken into account in the reference term by replacing the hard-chain contribution of the PC-SAFT model by a charged-hard-chain contribution. Moreover, counterion condensation is accounted for to determine the effective number of charges along the polyion as well as of free counterions. The electrostatic contribution of the free counterions is described by a Debye–Hückel term.     

Comparison on photo-initiators for the preparation of methacrylate monolithic columns for capillary electrochromatography

The synthesis of lauryl methacrylate monoliths for capillary electrochromatography by UV polymerization using several free-radical initiators (α,α′-azobisisobutyronitrile, 2,2-dimethoxy-2-phenylacetophenone, dibenzoyl peroxide (BPO) and lauroyl peroxide (LPO)) has been investigated. Using a 1,4-butanediol/1-propanol mixture as porogenic solvent, the influence of each initiator and its content on the morphological and electrochromatographical properties of beds was evaluated. Under their respective optimum content, satisfactory separations of a test mixture of PAHs with similar efficiencies (minimum plate heights of 8.0–12.7 μm obtained from Van Deemter plots) were achieved for the four investigated photo-initiators. The columns photo-polymerized with LPO provided the best compromise between chromatographic performance and analysis time. Moreover, this initiator showed a fine control in the column retention properties. The resulting monolithic columns exhibited a good run-to-run repeatability in the tested chromatographic parameters (RSD < 2.4%) for all initiators investigated; and satisfactory column-to-column repeatability (RSD < 6.0%), except for beds photo-polymerized with BPO (RSD < 10.8%).     

Transition-metal-free synthesis of polysubstituted pyrrole derivatives via [4 + 1] annulation of β-keto acids (C1 synthon) and α,β-unsaturated imines

A novel [4 + 1] annulation protocol for the synthesis of polysubstituted pyrrole derivatives from β-keto acids and α,β-unsaturated imines via a tandem Michael addition, decarboxylation and TBAI-catalyzed oxidative annulation has been developed. This method provides a new and facile application of β-keto acids as 1,1-nucleophilic/electrophilic type C1 synthons.