Synthesis of a series of vicinal diamines with potential biological activity

A broad range of vicinal diamines based on styrene oxide are synthesisedvia mixtures of regioisomeric amino alcohols. The ring opening of the intermediate aziridinium ions by primary amines proceeds with high regioselectivity, leading to the target diamines as single regioisomers for all reaction series. The compounds are of potential biological interest as ligands for cisplatin analogues. Anticancer activity tests of both groups of compounds are in progress.     

Microbial products. II. Granaticinic acid,a new antibiotic from a thermophilic streptomycete

Streptomyces sp. XT-11989 produces a mixture of two antibiotics with litmus-like indicator properties. One of them was shown to be identical with granaticin, the other was identified as [1S,3S,4S,7R,9R,10S,13R]-4,7,9,10-tetrahydro-5,12-dioxo-4, 6,10,11,13-pentahydroxy-1,9-dimethyl-(1H,3H)-7,10-ethanonaphtho[2,3-c: 6,7-c]dipyran-3-acetic acid and termed granaticinic acid. Microbial production and nuclear magnetic resonance data of these antibiotics are discussed and the antibacterial properties of the antibiotics are compared.

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Mikrobielle produkte. II. Granaticinsäure, ein neues Antibiotikum von einem thermophilen Streptomyceten

Zusammenfassung Der Streptomycetenstamm XT-11989 produziert eine Mischung von zwei Antibiotika mit Lakmus-ähnlichen Indikatoreigenschaften. Eines dieser Antibiotika erwies sich als Granaticin, das andere wurde als [1S,3S,4S,7R,9R,10S,13R]-4,7,9,10-tetrahydro-5,12-dioxo-4,6,10,11,13-pentahydroxy-1,9-dimethyl-(1H,3H)-7,10-ethanonaphto[2,3-c: 6,7-c]dipyran-3-essigsäure identifiziert und Granaticinsäure benannt. Mikrobiologische Produktion und Kernresonanzdaten dieser antibiotika werden besprochen und ihre antibakteriellen Eigenschaften verglichen.

     

Parallel synthesis of novel benzimidazoles on a soluble polymer support

Liquid phase combinatorial synthesis using a soluble polyethylene glycol (PEG) polymer support and commercially available 3-nitro-4-fluoro benzoic acid is carried out in order to create a molecular library of trisubstituted benzimidazoles. The PEG-ester conjugate of 3-nitro-4-fluoro benzoic acid is subjected to ipso-fluoro displacement by various primary amines. The nitro group is reduced under neutral conditions using excess zinc and ammonium chloride, producing the polymer-boundo-phenylene diamines. Reaction of the diamines with different aldehydes results in cyclisation to benzimidazoles. The polymer support is cleaved releasing the desired products in high yields and purity. All reactions are performed at room temperature.      

Thermal behavior of some aromatic copolyethers containing a propylenic spacer

The main objective of this paper is to study the thermal stability of some aromatic copolyethers containing a propylenic spacer. Some of the investigated copolyethers displayed a liquid crystalline (LC) behavior, with the presence of the mesogenic groups in the main chain, inducing high values of the thermal transition temperatures. As a consequence, a thermal stability study was necessary to establish the maximum temperature value for the LC behavior characterization. A thermal degradation mechanism is proposed, taking into consideration the azobenzenic unit as the weakest link in the polymer chain and thus, the starting point of the thermal degradation process. The degradation mechanisms were correlated with the chemical structure and the polarity and conformation of the chains. Conformational analysis was performed using molecular simulations. Freeman-Caroll and Coats-Redfern methods were used to calculate some kinetic characteristics.     

On the role of surface energy in the flattening of a crystal face

The question addressed in this paper is the flattening of the valley separating two growth hillocks emanating from screw dislocations during crystal growth. It is argued that both thermodynamic and kinetic effects contribute to this result, at least on a quasi-atomic scale. If performed under low enough supersaturation the growth leads to the formation of the face morphology corresponding to the minimum of the surface free energy. Accelerated step annihilation in the valley floor is a universal factor, which favors face flatting under any supersaturation. Based on the oral presentation during ICCG14, Grenoble, France, 09–13 August 2004.     

Application of a partially mobile model of monolayer adsorption to multilayer phenomena

Two multilayer adsorption models are discussed, assuming partially mobile adsorption in the first layer, and theBET orKim-Oh (KO) mechanisms for formation of higher layers. The theoretical multilayer adsorption isotherms corresponding to these models have been calculated for differing degrees of mobility of the first layer.

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Anwendung eines partiell mobilen Modells der Adsorption der ersten Schicht bei Mehrschicht-Phenomenen

Zusammenfassung Zwei Mehrschicht-Modelle, bei der Annahme einer partiell mobilen Adsorption der Erst-Schicht, und desBET, bzw.Kim-Oh (KO) Mechanismus für die Ausbildung höherer Schichten, werden diskutiert. Die theoretischen Mehrschicht-Adsorptionsisothermen, die diesen Modellen entsprechen, werden für verschiedene Grade von Mobilität der ersten Schicht berechnet.

     

麝香草的新单萜配糖物的分离与合成

从麝香草(Thymus vulgaris L)的甲醇萃取物中分离出三个单萜配糖物. 用核磁共振光谱确定了它们的结构为对伞花-9-基-β-D-葡糖苷(1), 5-β-D-葡糖苷百里氢醌(2)和2-β-D-葡糖苷百里氢醌(3). 其中1是新化合物, 用以对伞花-9-醇为原料的对映体选择性合成方法确定了化合物1的8位的立体化学为R型.     

Influence of a new axial impeller on K L a and xylanase production by Penicillium canescens 10-10c

The effects of a new axial impeller (HTPG4) on oxygen volumetric transfer coefficient, K _L a, and xylanase production by Penicillium canescens 10-10c were studied and compared for dual-impeller systems, one with one DT4 impeller below and one HTPG4 above (DT4-HTPG4) and one with two DT4 (DT4-DT4) impellers, in a 5-L bioreactor. The volumetric coefficient of oxygen transfer was measured in culture medium using a gassing-out method at different gassing rates and agitation speeds. We observed that the DT4-HTPG4 combination provided better K _L a performance than the DT4-DT4 combination. The two combinations were also tested for their influence on xylanase production by a filamentous microorganism; P. canescens 10-10c. These experiments demonstrated that the DT4-HTPG4 combination impeller enhanced enzyme production up to 23% compared with the DT4-DT4 combination at an aeration rate of 1 vvm and an agitation speed of 600 rpm. The main cause for this difference is thought to be a higher shear stress generated by the DT4-DT4 combination, which damages the mycelium of P. canescens and decreases xylanase production.     

Evidence for a novel mechanism of microbial cellulose degradation

There are two well studied mechanisms that are used by cellulolytic microorganisms to degrade the cellulose present in plant cell walls and a third less well studied oxidative mechanism used by brown rot fungi. The well studied mechanisms use cellulases to hydrolyze the β-1,4 linkages present in cellulose, however the way in which cellulases are presented to the environment are quite different for each mechanism. Most aerobic microorganisms secrete a set of cellulases outside the cell (free cellulase mechanism) while most anaerobic microorganisms produce large multi enzyme complexes on their outer surface (cellulosomal mechanism). Their genomic sequences suggest that the aerobic bacterium, Cytophaga hutchinsonii and the anaerobic bacterium, Fibrobacter succinogenes, do not use either of these mechanisms for degrading cellulose, as these organisms only code for normal endocellulases not for processive cellulases like exocellulases and processive endocellulases which are used in both of the well studied mechanisms.     

Periodic perturbations of a polymer

The reduction of the short range translational symmetry of a polymer chain (caused by, for example, the loss of an isoconformational structure) is accommodated as a periodic perturbation in a semi-empirical tight-binding LCAO calculation. Using the results of a calculation on an unperturbed chain in a perturbational mixing procedure an energy matrix can be calculated whose order is equal to (or even less than) that of the unperturbed structure. The method is applied to the generation of various chain conformations from all-trans polyacetylene and is shown to work successfully.     

Development and validation of a GC-MS method for rapid determination of galanthamine in Leucojum aestivum and Narcissus ssp.: a metabolomic approach

Galanthamine, an acetylcholinesterase inhibitor marketed as a hydrobromide salt for the treatment of Alzheimer's disease, is obtained from some Amaryllidaceae plants. A new method was developed and validated for its quantification by GC-MS in different plant sources: bulbs and leaves from Narcissus confusus; bulbs from N. pseudonarcissus cv. Carlton; and leaves and in vitro cultures from L. aestivum. Samples (50 mg) were extracted with methanol (1 mL) for 2 h, then aliquots of the extracts were silylated and analyzed by GC-MS. The calibration line was linear over a range of 15-800 μg galanthamine/sample, ensuring an analysis of samples with a content of 0.03-1.54% analyte referred to dry weight. The recovery was generally more than 95%. Good inter- and intra assay precision was observed (RSD < 3%). Principal component analysis of GC-MS chromatograms allowed discrimination of the plant raw material with respect to species, organs and geographical regions. The analytical method developed in this study proved to be simple, sensitive and far more informative than the routine analytical methods (GC, HPLC, CE and NMR), so it may be useful for quality control of plant raw materials in the pharmaceutical industry.     

Flow-injection analysis with a small cylindrical wire type electrode

An amperometric detector with a small thin mercury film electrode is described. The device demonstrates advantageous operational characteristics such as small dispersion (D<2) and “memory effect” (me<0.6%), extensive maximum sample frequency (msf −200 samples/h), and high sensitivity. It has been proven useful in flow-injection analysis at a constant potential under hydrodynamic conditions.     

Evaluation of a Hypocrea jecorina Enzyme Preparation for Hydrolysis of Tifton 85 Bermudagrass

Tifton 85 bermudagrass, developed at the ARS-USDA in Tifton, GA, is grown on over ten million acres in the USA for hay and forage. Of the bermudagrass cultivars, Tifton 85 exhibits improved digestibility because the ratio of ether- to ester-linked phenolic acids has been lowered using traditional plant breeding techniques. A previously developed pressurized batch hot water (PBHW) method was used to treat Tifton 85 bermudagrass for enzymatic hydrolysis. Native grass (untreated) and PBHW-pretreated material were compared as substrates for fungal cultivation to produce enzymes. Cellulase activity, measured via the filter paper assay, was higher for fungi cultivated on PBHW-pretreated grass, whereas the other nine enzyme assays produced higher activities for the untreated grass. Ferulic acid and vanillin levels increased significantly for the enzyme preparations produced using PBHW-pretreated grass and the release of these phenolic compounds may have contributed to the observed reduction in enzyme activities. Culture supernatant from Tifton 85 bermudagrass-grown fungi were combined with two commercial enzyme preparations and the enzyme activity profiles are reported. The amount of reducing sugar liberated by the enzyme mixture from Hypocrea jecorina (after 192 h incubation with untreated bermudagrass) individually or in combination with feruloyl esterase was 72.1 and 84.8%, respectively, of the commercial cellulase preparation analyzed under the same conditions.     

The investigation of a series of n-hydroxybenzoic acids (n=p, m, o) on a new surface enhanced Raman scattering active substrate

Ag nanoparticles, organized on indium tin oxide (ITO) surface, can act as a new surface enhanced Raman scattering (SERS) active substrate as well as a dry electrode. Compared with the traditional SERS-active substrate, its notable advantage is that the microcosmic changes of the film can be reflected by the SERS spectrum during the investigation of the film's electrical and other macroscopic characteristics. To illuminate the above-mentioned property of this new substrate, a series of n-hydroxybenzoic acids (n-HBA; n=p, m and o) was tested as probe molecules by SERS technique. These SERS spectra indicate that the significant changes of frequencies as well as intensities, respectively, arise from the changes of the adsorption behavior along with the proportional variation of molecules and silver nanoparticles. Excellent SERS signals prove that the silver nanoparticles-coated ITO is a highly SERS-active substrate and can efficiently reflect the microcosmic property of the film, which suggest it has promising potential of being a new technique for further application in the field of thin-film research.     

Rational design and convenient synthesis of a novel family of ruthenium complexes with O,N-bidentate ligands

A two step procedure for the synthesis of a novel family of homogeneous and immobilized Ru-complexes containing Schiff bases as O,N-bidentate ligands is described. The new Ru-complexes have been structurally characterized by IR, Raman,¹H-,¹³C-NMR spectroscopy. The Schiff bases were associated with a diversity of inorganic and organic ligands such as chloride, phosphane, arenes, various carbenes (alkylidene, vinylidene, indenylidene and allenylidene as well as N-heterocyclic carbenes) and cyclodienes. By choosing a selective range of substituents for the Schiff base, useful physical and chemical properties of the prepared Rucomplexes can be induced. This synthetic approach is promising in creating a valuable and diverse selection of Ru-complexes, valuable for future applications.     

Chemistry of Indolopyridines with a Bridgehead Heteroatom. (Review)

Published data on the synthesis and reactions of indolopyridines with one bridgehead heteroatom and their benzannelated derivatives are reviewed for the first time.     

Gangliosides from the starfishEvasterias echinosoma: identification of a disialoganglioside containing 8-O-methyl-N-acetylneuraminic acid andN-formylgalactosamine

Gangliosides were isolated from the starfishEvasterias echinosoma and their structures were elucidated by chemical and physicochemical methods. Two major gangliosides were found to be disialogangliosides, whose carbohydrate chain is based on the trisaccharide β-N-acylgalactosaminyl-(l→3)-β-galactosyl-(l→4)-β-glucose (acyl is formyl or acetyl), both residue at of 8-O-methyl-N-acetylneuraminic acid being attached to theN-acylgalactosamine residue at positions 3 and 6. The minor components are disialogangliosides with linear carbohydrate chains in which the terminal sialic acid residue is attached to the penultimateN-acetylneuraminic acid residue at positions 4, 8, or 9. The lipid part of the gangliosides consists of sphingenine and unsubstituted fatty acids (mainly, palmitic and stearic acids). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 156–161, January, 2000.     

Aerogel nanoscale magnesium oxides as a destructive sorbent for toxic chemical agents

An autoclave hypercritical drying procedure has been used to prepare precursors of MgO from Mg(OCH₃)₂. This material was prepared with a specific surface area of 1200 m² g ¹. The dehydrated materials consisted of much smaller crystallites than conventionally prepared MgO and were free of OCH₃ groups. The precursors and samples of magnesium oxide were taken for experimental evaluation of their reactivity with mustard. The largest percentage of the conversion mustard into non-toxic products after the elapse of the reaction was 77%.     

Derivatives of phosphorous acid as a new class of ligands for Pd-catalyzed allylation

Amido- and aminophosphites and hydrospirophosphoranes can be used as ligands in the Pd-catalyzed allylation of ethyl malonate with ethyl (3-phenylprop-2-enyl) carbonate. Bidentate ligands (RO)₂P--O(CH₂)_n--NR"₂ (n = 2 and 3) were found to be the most effective ligands.