Unusual octalactones from Corynespora cassiicola, an endophyte of Laguncularia racemosa

Chemical investigation of the EtOAc extract of the mangrove-derived endophyte Corynespora cassiicola, isolated from Laguncularia racemosa (Combretaceae), afforded five new secondary metabolites, named coryoctalactones A–E (1–5). The structures of the new compounds were determined on the basis of 1D- and 2D-NMR spectroscopy as well as high-resolution mass spectrometry. The absolute configuration of the side chain in 1–3 and 5 were tentatively deduced based on biogenetic consideration in comparison with xestodecalactones, previously isolated from C. cassiicola. All isolated compounds were evaluated for their antimicrobial, cytotoxic, and antitrypanosomal activities.     

NOVEL SUPRAMOLECULAR DERIVATIVES CONTAINING TWO R3Sn+ (R = Me,n-Bu,or Ph) CONNECTING UNITS: THE FORMATION OF NOVEL HOST–GUEST SYSTEMS BY THE FACILE ENCAPSULATION OF GUEST THIOPHENE COMPOUNDS

New supramolecular complexes [(Me ₃ Sn)(Ph ₃ Sn) ₂ Fe(CN) ₆ ] (I) and [(n-Bu ₃ Sn)(Ph ₃ Sn) ₂ Fe(CN) ₆ ] (II) are readily accessible by straightforward self-assembly of [Fe(CN) ₆ ] ^3? and hydrated R ₃ Sn⁺/R′ ₃ Sn ⁺ ions (R = Ph, and R′ = Me or n-Bu). The structural characterization of (I) and (II) is compared with well-documented supramolecular complex containing only Ph ₃ Sn ⁺ unit, [(Ph ₃ Sn) ₃ Fe(CN) ₆ ]. These novel compounds have wide internal cavities capable of encapsulating voluminous organic compounds, and they behave as host acceptors forming charge transfer complexes (CTC). Thiophene compounds acting as guest donor species are encapsulated within the cavities of the three-dimensional (3D) supramolecular hosts. The structure and physical properties of these hosts and host–guest systems were studied by X-ray powder diffraction, IR, UV/Vis., and magnetic measurements.     

Efficient Approach for the Synthesis of Novel Functionalized Isoxazolines from Limonene

New functionalized isoxazolines were effeciently and easily prepared from limonene. The procedure involves a peri‐ and regioselective 1,3‐dipolar cycloaddition of nitrile oxides on the monoterpene external double bond, followed by a highly chemoselective RuCl₃‐NaIO₄ oxidative cleavage of the internal one. All the newly prepared isoxazolyl‐ketoacids were fully characterized from their spectroscopic data.     

Light-induced isotopic exchange between O2 and semiconductor oxides, a characterization method that deserves not to be overlooked

This article first indicates the various types of temperature-induced oxygen isotopic exchange (OIE) that can occur between labeled gaseous O₂ and solid oxides. Earlier main results of light-induced OIE with semiconductor oxides are then briefly reviewed. The core of the article reports new results about the use of light-induced OIE to assess (i) the lability of TiO₂ surface O atoms, as altered by calcination or Se deposits, via the comparison of OIE with the photocatalytic removal of methanol in air and (ii) the accessibility of TiO₂ affixed on a fiberglass material by means of a silica binder. Both this overview and these novel results illustrate the interest of OIE in heterogeneous photocatalysis.     

Synthesis of 5-azaindolizine derivatives by the palladium-catalyzed intermolecular formal [3+2] cycloaddition of alkylidenecyclopropanes with 1,2-diazines

The palladium-catalyzed formal [3+2] cycloaddition reaction of alkylidenecyclopropanes with 1,2-diazines proceeded smoothly to give the corresponding 5-azaindolizine derivatives in good to allowable yields. For example, in the presence of 5 mol % of Pd(PPh(3))(4), the reaction of 1-propylhexylidenecyclopropane with phthalazine or with pyridazine proceeded at 120 degrees C without solvent, and the corresponding 2-(1-butylpentyl)pyrrolo[2,1-a]phthalazine or 6-(1-butylpentyl)pyrrolo[1,2-b]pyridazine was obtained in 61% or 49% yield, respectively.     

基于氨基酸的Cu(Ⅱ)-色氨酸MOF催化剂上环氧化物与CO2环加成反应

由天然的/生物单元(氨基酸)构成的金属有机框架材料(MOFs)具有自然属性和丰富的酸/碱位和官能团,因而可用于CO2化学中.本文报道了氨基酸系含铜MOF(CuTrp,Trp = L-色氨酸)的催化效率.以甲醇为溶剂,在室温采用直接混合法合成了CuTrp催化剂,该方法具有很高的能量效率.采用X射线衍射、红外光谱、热重分析、电感耦合等离子体发射光谱法、扫描电镜和BET分析等手段对该催化剂进行了表征.采用环氧化物与CO2环加成制备环状碳酸酯反应评价了CuTrp催化剂活性.结果表明,在无溶剂条件下,CuTrp 催化剂可与四丁基溴化铵助催化剂发生协同作用.通过条件实验确定了优化的反应条件,并基于该实验结果和前期的密度泛函理论计算结果提出了反应机理.另外,CuTrp 催化剂在水中也表现出令人满意的稳定性,可重复使用三次以上而活性无明显下降.     

Development and validation of a reversed‐phase HPLC method for the determination of γ‐tocotrienol in rat and human plasma

γ‐Tocotrienol (γ‐T3) is a member of the vitamin E family. Recently, γ‐T3 has attracted the attention of the scientific community due to its potent anticancer activity and other therapeutic benefits. The objective of this study was to develop and validate a simple and practical reversed‐phase HPLC method with satisfactory sensitivity for the routine quantification of γ‐T3 in rat and human plasma. The separation of γ‐T3 from the plasma components was achieved with a C₁₈ reversed‐phase column with an isocratic elution using a mixture of methanol, ethanol and acetonitrile (85:7.5:7.5, v/v/v) with a UV detection at 295 nm. γ‐T3 was extracted from rat and human plasma by liquid–liquid extraction with an average recovery of 60%. The method proved linear in the range 100–5000 ng/mL. The inter‐day precision ranged from 5.8 to 12.8% and the accuracy ranged from 92.4 to 108.5%, while the intra‐day precision ranged from 0.7 to 7.9% in both rat and human plasma. This data confirm that the developed method has a satisfactory sensitivity, accuracy and precision for the quantification of γ‐T3 in plasma. To assess its applicability the method was successfully applied to the quantitative analysis for pharmacokinetic studies of γ‐T3 in rats administered a 10 mg/kg single oral dose. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of a soliton in a medium

The solution of the sine-Gordon equation for a medium is studied in a simplified “quasi-linear” approximation. Several aspects of this approximation are explored and compared with other approximate solutions for the sine-Gordon soliton.     

Fokker-Planck equation for a periodic potential

The Fokker-Planck equation in one dimension has been solved for a system in a periodic potential and linearly perturbed by a time- and space- varying external electric field. The solution is not exact, but we believe it is less approximate than any attempted previously on this problem. We have calculated the frequency and wave-vector dependent mobility and discussed its behaviour in some limiting cases.The application of our model to various physical situations is discussed.     

Minimal degree univariate piecewise polynomials with prescribed Sobolev regularity

For $k\in \{1,2,3,\dots \}$, we construct an even compactly supported piecewise polynomial ${\psi }_k$ whose Fourier transform satisfies $A_k{(1+{\omega }^2)}^{?k}\le {\stackrel{?}{\psi }}_k\left(\omega \right)\le B_k{(1+{\omega }^2)}^{?k}$, $\omega \in \mathbb{R}$, for some constants $B_k\ge A_k>0$. The degree of ${\psi }_k$ is shown to be minimal, and is strictly less than that of Wendland’s function ${?}_{1,k?1}$ when $k>2$. This shows that, for $k>2$, Wendland’s piecewise polynomial ${?}_{1,k?1}$ is not of minimal degree if one places no restrictions on the number of pieces.