On Attempted Oxidative Cyclisation of Isomeric N,N'-Diphenylphenylenediamines and Their N,N'-Dimethyl Derivatives by Palladium(II) Acetate and Uv Light

The cyclisation of N,N'-diphenyl-o-, m- and p-phenylenediamines and their N,N'-dimethyl derivatives by palladium(II) acetate and UV light separately led to both bis-cyclisation, furnishing indolocarbazoles, and mono-cyclisations with cleavage as well as retention of one substituent, producing substituted carbazoles.     

The use of Cu and Zn salicylaldimine complexes as catalyst precursors in ring opening polymerization of lactides: ligand effects on polymer characteristics

A range of monomeric tetra‐coordinate copper (II) and zinc (II) complexes based on N,O‐bidentate salicylaldimine Schiff base ligands has been synthesized and characterized using various spectroscopic techniques. These complexes were then evaluated as initiators in ring‐opening polymerization of lactides at both 70 °C and 110 °C. The effect of structural changes in the complexes on the ability of these compounds to initiate lactide polymerization as well as the impact on the chemical and physical characteristics of the polymers obtained indicate that the coordination geometry of the metal complex, M? O bond length and substituents on the Schiff base ligand all play a role in the catalyst activity. Electronic factors were dominant in the case of the copper complexes while steric factors prevailed in the case of Zn initiators. Both the Zn and Cu complexes exhibit characteristics of living ring opening polymerization. Copyright © 2010 John Wiley & Sons, Ltd.     

Total synthesis of biselide A

A total synthesis of the marine macrolide biselide A is described that relies on an enantiomerically enriched α-chloroaldehyde as the sole chiral building block. Several strategies to construct the macrocycle are presented including a macrocyclic Reformatsky reaction that ultimately provides access to the natural product in a longest linear sequence of 18 steps. Biological testing of synthetic biselide A suggests this macrolide disrupts cell division through a mechanism related to the regulation of microtubule cytoskeleton organization. Overall, this concise synthesis and insight gained into the mechanism of action should inspire medicinal chemistry efforts directed at structurally related anticancer marine macrolides.

A total synthesis of the marine macrolide biselide A is described that relies on an enantiomerically enriched α-chloroaldehyde as the sole chiral building block.     

Headspace single-drop microextraction and cuvetteless microspectrophotometry for the selective determination of free and total cyanide involving reaction with ninhydrin

Headspace single-drop microextraction has been used for the determination of cyanide with ninhydrin in combination with fibre-optic-based cuvetteless microspectrophotometry which accommodates sample volume of 1 μL placed between the two ends of optical fibres, and has been found to avoid salient drawbacks of batch methods. This method involved hydrocyanic acid formation in a closed vial, and simultaneous extraction and reaction with 2 μL drop of ninhydrin in carbonate medium suspended at the tip of a microsyringe needle held in the headspace of the acidified sample solution. The method was linear in range 0.025-0.5 mg L⁻¹ of cyanide. The headspace reaction was free from the interference of substances, e.g., thiocyanate, hydrazine sulphate, hydroxylammonium chloride and ascorbic acid. Sulphide was masked by cadmium sulphate, nitrite by sulphamic acid, sulphite by N-ethylmaleimide, and halogens by ascorbic acid. The limit of detection was found to be 4.3 μg L⁻¹ of cyanide which was comparable to existing most sensitive methods for cyanide. However, the present method is far more simple. The method was applied to acid-labile and metal cyanides complexes by treatment with sulphide when metal sulphides were precipitated setting cyanide ion free, and to iron(II) and (III) cyanide complexes by their decomposition with mercury(II), the mercury(II) cyanide formed was then determined. These pre-treatment methods avoided cumbersome pre-separation of cyanide by methods such as distillation or gas diffusion. The overall recovery of cyanide in diverse samples was 97% with RSD of 3.9%.     

Magnetic transport behavior of nanocrystalline Nd0.67A0.33MnO3 (A = Ca,Sr, Pb and Ba)

Nanocrystalline A-doped manganites, with compositional formula, Nd_0.67A_0.33MnO₃ (A = Ca, Sr, Pb and Ba) were prepared by Polyvinly Alcohol (PVA) gel route. After characterizing the samples by X-ray diffraction studies and by measuring electrical, magnetic transition temperatures, a systematic investigation of magnetization and magnetoresistance measurements both as a function of magnetic field and temperature was undertaken. The variation of electrical and magnetic transition temperatures is explained on the basis of size variance parameter. It has been concluded from the M–H plots that NCMO, NPMO and NBMO samples are exhibiting narrow hystersis loops indicating soft ferromagnetic nature, while the NSMO is found to exhibit double hystersis loop indicating the presence of metamagnetic transition. It is also observed that among the four samples, Nd_0.67Ca_0.33MnO₃ is found to exhibit the highest magnetoresistance (MR) of 91% over a broad temperature region.     

Syntheses and crystal structures of gadolinium and europium complexes of AAZTA analogues

Modified 6-amino-6-methylperhydro-1,4-diazepinetetraacetic acid (AAZTA) ligands with a hydroxyl arm have been synthesized and characterized. The crystal structures of its lanthanide complexes, determined by single crystal X-ray crystallography, show centrosymmetric nonacoordinated dimeric M₂L₂ forms where one carboxylate group from each ligand forms a bridge between two metal centers. Each metal center is coordinated with one inner sphere water molecule. The hydroxyl arm does not interfere in the coordination environment of the metal and therefore acts as a good anchor for attaching other functional motifs.     

Formal total synthesis of borrelidin: synthesis of C1-C11 fragment via desymmetrization strategy

A stereoselective formal total synthesis of borrelidin is described. The synthetic strategy for synthesis of C1-C11 fragment features desymmetrization of Diels-Alder adduct, Sharpless asymmetric epoxidation, regioselective opening of chiral epoxide, and alkylation using Evans chiral auxiliary.     

Lomustine loaded chitosan nanoparticles: characterization and in-vitro cytotoxicity on human lung cancer cell line L132

The aim of this work was to prepare chitosan nanoparticles loaded with antineoplastic drug Lomustine (LCNPs), by ionic-gelation method with homogenization. The nanoparticles were characterized for particle size, polydispersity index (PDI), surface morphology, encapsulation efficiency, in-vitro drug release and cytotoxicity on human lung cancer cell line L132 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The particle size, zeta potential and encapsulation efficiency of prepared nanoparticles ranged from 75 ± 1.1 to 637 ± 1.6 nm (PDI from 0.05 ± 0.001 to 0.18 ± 0.007), 37.2 ± 0.21 to 53.8 ± 0.18 mV and 66.74 ± 1.4 to 98.0 ± 1.8% respectively. The particles were spherical in shape with smooth surface in scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Mechanical shearing by homogenization treatment significantly changed the nanoparticle size. The drug release rate was biphasic and diffusion controlled over the 8 h. LCNPs greatly inhibited the growth of the L132 cancer cell line used in this study in comparison to the native Lomustine (LMT).     

Production of Acid-Stable and High-Maltose-Forming α-Amylase of Bacillus acidicola by Solid-State Fermentation and Immobilized Cells and Its Applicability in Baking

Among matrices used for immobilizing Bacillus acidicola cells [calcium alginate, chitosan + alginate, scotch brite, and polyurethane foam (PUF)], ??-amylase production was highest by PUF-immobilized cells (9.1?U?ml^?1), which is higher than free cells (7.2?U?ml^?1). The PUF-immobilized cells could be reused over seven cycles with sustained ??-amylase production. When three variables (moisture, starch, and ammonium sulfate), which significantly affected enzyme production in solid-state fermentation (SSF), were optimized using response surface methodology, 5.6-fold enhancement in enzyme production was attained. The enzyme production in SSF is 3.8-fold higher than that in submerged fermentation. The bread made by supplementing dough with ??-amylase of B. acidicola scored better than those with the xylanase of Bacillus halodurans and thermostable ??-amylase of Geobacillus thermoleovorans.