Semisynthesis of (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid

This paper describes the use of zamoranic acid in the first semisynthesis of the furolabdane (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid, which also establishes the absolute configuration of the natural product. Direct deconjugation of Δ⁷ in zamoranic acid and Bestmann methodology for the furan ring synthesis are the key steps.     

Magnetic and thermal analysis of <Emphasis Type="Italic">M</Emphasis>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> (<Emphasis Type="Italic">M</Emphasis> = Co,Mn, Zn) nanoparticles

Magnetic nanoparticles were prepared by a wet chemical method. Precursors of MFe₂O₄ (M = Co, Mn, Zn) were prepared from a mixture of metal chloride and metasilicate nonahydrate aqueous solutions. The precipitates obtained in the wet chemical method were calcined to obtain MFe₂O₄ nanoparticles encapsulated by amorphous SiO₂. The blocking temperatures T _B’s were between 20 and 320 K, in this temperature range, the anisotropy energy of the particles decreased below their thermal energy. T _B increased with the particle size. In order to clarify the nanoparticle formation process, differential thermal analysis and thermogravimetric (TG-DTA) measurements were performed for the as-prepared samples.     

A Multiplicity Result for an Elliptic Anisotropic Differential Inclusion Involving Variable Exponents

In this paper we are concerned with the study of a class of quasilinear elliptic differential inclusions involving the anisotropic $\overrightarrow {p}(\cdot)$ -Laplace operator, on a bounded open subset of ${\mathbb R}^n$ which has a smooth boundary. The abstract framework required to study this kind of differential inclusions lies at the interface of three important branches in analysis: nonsmooth analysis, the variable exponent Lebesgue–Sobolev spaces theory and the anisotropic Sobolev spaces theory. Using the concept of nonsmooth critical point we are able to prove that our problem admits at least two non-trivial weak solutions.     

Lysozyme binding onto cat-anionic vesicles

Mixing aqueous sodium dodecylsulfate with cetyltrimethylammonium bromide solutions in mole ratios close to (1.7/1.0) allows the formation of cat-anionic vesicles with an excess of negative charges on the outer surface. The vesicular dispersions are mixed with lysozyme, and interact electrostatically with the positive charges on the protein, forming lipo-plexes. Dielectric relaxation, zeta-potential, and light scattering indicate the occurrence of interactions between vesicles and the protein. According to CD, the vesicle-adsorbed protein retains its native conformation. Binding and surface saturation, inferred by dielectric relaxation and zeta-potential, fulfil a charge neutralisation stoichiometry. Adsorbed lysozyme promotes the vesicle clustering and is concomitant with the lipo-plexes flocculation. Above the charge neutralisation threshold, lysozyme in excess remains dispersed in molecular form. Attempts were made to determine in what conditions protein release from the vesicles occurs. Accordingly, the full neutralisation of sodium dodecylsulfate in excess by cetyltrimethylammonium bromide ensures the lipo-plexes break-up, the precipitation of the mixed surfactants and the protein release in native form.     

Structure and property studies of hybrid xerogels containing bridged positively charged 1,4-diazoniabicycle[2.2.2]octane dichloride

The compound di-3-n-propyltrimethoxysilane (1,4-diazoniabicycle[2.2.2]octane) dichloride, [(MeO)3Si(CH2)3N+ (CH2CH2)3N+ (CH2)3Si(OME)3]Cl2 was obtained and was used as a precursor reagent to obtain hybrid xerogels where the organic molecule was bonded to a silica framework by reacting the ends of both sides of the precursor reagent. That is, both -Si(OME)3 groups react with tetraethylorthosilicate (TEOS) by hydrolysis-condensation reactions. The resulting hybrid xerogels with variable C/Si mole ratios were prepared and analyzed and their textural characteristics determined. The samples prepared presented micropores with diameter 1.5 nm, the chain length of which matched with the estimated length of the organic bridging group. The charged organic bridging groups allow the immobilization of hexacyanoferrate ions by an ion exchange process. The electron transfer process of the hexacyanoferrate anionic complex confined in the pores of the matrices was studied by cyclovoltammetry.     

Molecular diffusion in liquid crystals and chiral discrimination. II. Model calculations

We perform model calculations of the macroscopic diffusion coefficient for a solute moving in a chiral nematic (cholesteric) liquid crystal (LC) phase applying the methodology developed by Frezzato et al. [J. Chem. Phys. 122, 164904 (2005)]. Three types of solutes with different features are studied: ellipsoid [roto-translational coupling (RTC) absent], bent rod (RTC present), and two-blade propeller (with RTC and chiral shape). For each prototype molecule we estimate the effect of cholesteric helix pitch and local order on the diffusion along the helix axis. For the ellipsoidal particle we find that translational diffusion is slowed down by rotation around the short axis. For the chiral solute we show that the enantiomer with shape chirality opposite to that of the LC phase is slowed down more than the other. This provides a proof of principle of the possibility of separating the two enantiomers via transport in a suitable chiral medium.     

Synthesis of quinone/hydroquinone sesquiterpenes

ent-Halimic acid has been used in the synthesis of the quinone/hydroquinone sesquiterpenes (−)-aureol, (−)-smenoqualone, (−)-neomamanuthaquinone and in the formal synthesis of (−)-cyclosmenospongine.