Recent developments in the combinatorial synthesis of nitrogen heterocycles using solid phase technology

Recognizing the potential of combinatorial chemistry to accelerate drug discovery and development, most pharmaceutical and related industries are seriously looking toward combinatorial synthesis of compounds in order to facilitate the identification of 'lead' molecules. In particular, solid phase synthesis is the core technology for combinatorial chemistry and is widely used for generating libraries of structurally related compounds. Since many drugs contain the nitrogen heterocyclic component and since heterocycles possess a high order of structural diversity, a precise overview of recent progress in the combinatorial synthesis of nitrogen heterocycles using solid phase methodology would be useful. Since the progress in solid phase synthesis of organic molecules has been reviewed regularly from 1992 to 1998, only the development of solid phase combinatorial synthetic approaches of small nitrogen heterocycles since 1999 will be reviewed here. This review describes the solid phase synthesis of azepanes, benzodiazepines, benzimidazoles, benzothiazepines, cinnolines, indolizines, beta lactams, oxazepins, oxazoles including benzisooxazoles, hydantoins, piperidines, pyrimidines, pyrazolones, quinolones, trizolopyridazines and thiazoles.     

Synthesis of some new 4-imino-3,5,7-trisubstituted-pyrido[2,3-d]pyrimidine-2(1H)-thiones

The synthesis of 4-imino-3,5,7-trisubstituted-pyrido[2,3-d]pyrimidine-2(1H)-thiones is described. The elemental analysis, ir and nmr spectral data confirm the structure of the products.     

Electro-kinetic transport of acetone,water and their binary mixtures

Summary Electroosmosis of acetone, water and their binary mixtures through thorium oxide (ThO₂) plug membrane has been studied and the data analysed using non-equilibrium thermodynamics. The phenomenological coefficients,L ₁₁ andL ₁₂ have been found to vary nonlinearly with composition. Excess phenomenological coefficients have therefore been evaluated and the results explained in terms of the membrane permeant and permeant-permeant interactions. The results on the measurement of electrophoretic velocity of ThO₂ particles dispersed in acetone-water mixtures also lead to the conclusion that the components of the mixture interact appreciably.

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Zusammenfassung Die Elektroosmose von Aceton, Wasser and deren binären Gemische durch eine ThO₂-Pflock-Membran wurde untersucht; die Daten wurden mit Hilfe der Nichtgleich-gewichts-Thermodynamik analysiert. Die phänomenologischen KoeffizientenL ₁₁ undL ₁₂ ändern sich hiernach nichtlinear mit der Zusammensetzung. Es wurden daher Exzess-L ₁₁-und -L ₁₂-Werte berechnet; die Ergebnisse wurden auf Grund der Membran-Permeant- und Permeant-Permeant-Wechselwirkungen diskutiert. Aus der Messung der elektrophoretischen Geschwindigkeit von ThO₂-Teilchen, die in Aceton-Wasser-Gemischen dispergiert sind, folgt, daß eine merkliche Wechselwirkung zwischen den Komponenten der Mischung vorliegt.

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With 8 figures and 1 table     

A simple procedure for the chromatographic isolation and determination of prostaglandins from human seminal plasma

Summary A relatively simple procedure for the isolation and determination of the prostaglandins present in human seminal fluid is described. It involves preliminary chromatographic purification of these compounds from the major non-prostaglandin impurities followed by their total elution in one solvent (one-step elution). The prostaglandins thus obtained were almost free from other lipids and were further resolved into prostaglandin-groups and individual prostaglandins by repeated thin-layer chromatography. Data are also presented for prostaglandin contents of fresh semen samples from five individuals and results compared with those from the stored samples.

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Einfaches Verfahren zur chromatographischen Isolierung und Bestimmung von Prostaglandinen aus menschlichem Sperma

Zusammenfassung Das Verfahren umfaßt eine chromatographische Abtrennung der Verbindungen von den hauptsächlichsten Verunreinigungen und die Gesamtelution mit einem Lösungsmittel. Die von anderen Lipiden fast völlig freien Prostaglandine werden durch wiederholte Dünnschicht-Chromatographie in Gruppen und Einzelverbindungen getrennt. Werte werden angegeben über die Prostaglandingehalte von frischem im Vergleich zu gelagertem Sperma.

     

Keggin ion mediated synthesis of hydrophobized Pd nanoparticles for multifunctional catalysis

Development of simple and reliable protocols for the synthesis of organically soluble catalytically active metal nanoparticles is an important aspect of research in nanomaterials. We demonstrate herein the formation of Pd nanoparticles by reduction of aqueous Pd(NO(3))(2) by photoexcited Keggin ions (phosphotungstate anions). This results in the formation of Pd nanoparticles capped with with Keggin ions that render the particles negatively charged. The Keggin ion capped Pd nanoparticles may then be phase transferred into nonpolar organic solvents such as toluene by electrostatic complexation with cationic surfactants such as octadecylamine at the liquid-liquid interface. This results in a new class of catalyst wherein both the Pd core and Keggin ion shell may be used in a range of catalytic reactions leading to a truly multifunctional catalyst dispersible in organic solvents.     

Cumulative yields of short-lived isotopes of barium in the spontaneous fission of252Cf

Cumulative yields of short-lived/barium isotopes^{139, 141, 142}Ba have been determined in the spontaneous fission of²⁵²Cf, using fast radiochemical separation and gamma-ray spectrometry.¹⁴²Ba yield is reported for the first time. The measured cumulative yields are converted to chain yields, assuming normal charge distribution systematics for comparision with the literature data.     

Cumulative yields of the short-lived ruthenium isotopes in the spontaneous fission of252Cf

⁶⁷Ga is produced by the⁶⁶Zn(d,n) reaction at 9 MeV bombarding energy. Deuterons of about 30 A obtained from the T-11 Tandem accelerator are used to bombard targets of natural Zinc prepared by electroplating onto thick copper disks. Radiochemical separation of gallium is performed by using a cation exchange column. The optimum conditions for an efficient separation are given in detail.     

Role of partially flocculated sols in emulsion stability

Summary The stability of emulsion of Toluene in water stabilized by partially flocculated ferric hydroxide sol has been studied. The size of the emulsion droplets as determined by size frequency analysis is found to be of 1.1 μ radius. The flocculation studies were carried out haemocytometrically at different amount of electrolytes and at different p_H values. The electrokinetic potential ‘ζ’ was determined micro-electrophoretically at different amounts of electrolytes and also at different p_H's. In the case of tri and tetra valent anions the charge reversal was observed. In the light of the D.V.O. theory the interaction energy profiles were drawn and 2–6 kT deep secondary minima obtained showing thereby the occurrence of reversible flocculation. Degree of aggregation has been calculated theoretically at different values of ‘A’ and the value of A was found to be 1.0×10⁻¹² erg to fit the value of degree of aggregation obtained haemocytometrically. The charge densities and binding parameters have also been calculated.     

Comparison of compositional and morphological atom-probe tomography analyses for a multicomponent Fe-Cu steel.

A multicomponent Fe-Cu based steel is studied using atom-probe tomography. The precipitates are identified using two different methodologies and subsequent morphological and compositional results are compared. The precipitates are first identified using a maximum separation distance algorithm, the envelope method, and then by a concentration threshold method, an isoconcentration surface. We discuss in detail the proper selection of the parameters needed to delineate precipitates utilizing both methods. The results of the two methods exhibit a difference of 44 identified precipitates, which can be attributed to differences in the basis of both methods and the sensitivity of our results to user-prescribed parameters. The morphology of the precipitates, characterized by four different precipitate radii and precipitate size distribution functions (PSDs), are compared and evaluated. A variation of less than approximately 8% is found between the different radii. Two types of concentration profiles are compared, giving qualitatively similar results. Both profiles show Cu-rich precipitates containing Fe with elevated concentrations of Ni, Al, and Mn near the heterophase interfaces. There are, however, quantitative disagreements due to differences in the basic foundations of the two analysis methods.     

Competitive adsorption behavior of heavy metals on kaolinite

Polluted and contaminated soils can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a soil system will be affected by the presence of other metals. In this study we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto kaolinite in single- and multi-element systems as a function of pH and concentration, in a background solution of 0.01 M NaNO3. In adsorption edge experiments, the pH was varied from 3.5 to 10.0 with total metal concentration 133.3 microM in the single-element system and 33.3 microM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH50 (the pH at which 50% adsorption occurs) was found to follow the sequence Cu相似文献