Tetrakis(imidazolyl)borate-based coordination polymers: group II network solids,M[B(Im)4]2(H2O)2 (M = Mg,Ca, Sr)

We are using the coordinating anion tetrakis(imidazolyl)borate to construct new metal-organic framework structures. In this report, we present three alkaline earth metal network solids incorporating this anion. All three compounds have the same formula, M[B(Im)(4)](2)(H(2)O)(2) (M = Mg, Ca, Sr), and the same coordination environment about the metal. However, the three compounds have different network structures with different degrees of hydrogen bonding; the Mg material forms a two-dimensional network and the Ca and Sr compounds form one-dimensional chains. In addition, we present the structure of the protonated anion B(HIm)(Im)(3) as a model for the default structure of this anion and discuss how the conformation of tetrakis(imidazolyl)borate can affect the structure of network solids.     

Expert systems for method development and validation in HPLC

ESCA, Expert Systems Applied to Chemical Analysis, started its research in March 1987, with the aim of building prototype expert systems for HPLC method development. Results of this research have been published as the work has progressed. The project is now completed and this paper summarises some of the overall project conclusions. Seven different expert systems have been built which tackle problems throughout the process of method development, four stand-alone systems and three integrated systems. The object of ESCA was to evaluate the applicability of expert system technology to analytical chemistry and not all the systems were built for commercial uses. Many of the systems tackle problems specific to one or more of the partners and thus may not be useful outside this environment. However, the results of the work are still pertinent to analysts wishing to build their own systems. These results are described, however, the emphasis of the paper is on those systems developed for method validation.Method validation for HPLC is a complex task which requires many characteristics of the method to be tested, e.g. accuracy, precision, etc. The expert systems built within ESCA concern the validation of precision. Two systems were developed for repeatability testing and ruggedness testing. The method validation process can be divided into several discrete stages, these include: (1) The selection of the method feature to test, for instance which factors can influence the ruggedness of a method. (2) The definition of a test procedure, for instance an efficient statistical design. (3) The execution of experiments and the interpretation of results. (4) A diagnosis of any observed problem. This paper describes these two systems in some detail and summarises some of the results obtained from their evaluation. It concludes that expert systems can be useful in solving analytical problems and the integration of several expert systems can provide extremely powerful tools for the analyst.     

Synthesen von Heterocyclen, 79. Mitt.: Über Reaktionen mit Ketensäurechloriden

Zusammenfassung Monosubstituierte Malonsäurechloride reagieren mit Nitrilen bzw. Isocyanaten zu 1,3-Oxazinen¹. Malonylchlorid setzt sich mit den gleichen Reaktionspartnern sowie mit Phenylsenföl in einer komplizierteren Reaktionsfolge zu bicyclischen Pyrono-1,3-oxazinen^1–3 um.

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Monosubstituted malonyl chlorides react with nitriles and isocyanates to 1.3-oxazines. Malonyl chloride itself reacts with nitriles, isocyanates, and iso-thiocyanates in a complicated manner yielding bicyclic pyrono-1.3-oxazines.

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Herrn KollegenA. Wacek, Techn Hochschule Graz, mit den besten Wünschen zum 70. Geburtstag.     

Decrease in langerhans cells and increase in lymph node dendritic cells following chronic exposure of mice to suberythemal doses of solar simulated radiation

Exposure of certain strains of mice to ultraviolet radiation (UVR) causes suppression of some innate and adaptive immune responses. One such consequence of acute UVB exposure is a reduction in the number of Langerhans cells (LC) in the epidermis and an increase in dendritic cells (DC) in lymph nodes draining the irradiated skin sites. Exposure to chronic UVB irradiation also has effects on the immune system, but it is unknown what effects are caused by repeated doses of solar simulated radiation (SSR). Consequently, the main aims of the present study were to determine whether repeated exposure to low doses of SSR would lead to similar changes in these cell populations and whether chronic doses of SSR activate a protective photoadaptation mechanism. Groups of C3H/HeN mice were irradiated daily with 3.7 J/cm(2) SSR from Cleo Natural lamps for 2, 10, 20, 30 or 60 days. Further groups of mice received an additional dose of 7.4 J/cm(2) SSR on days 2, 10, 30 or 60 to test for photoadaptation. The numbers of LC in the epidermis and DC in the lymph nodes draining irradiated skin sites were counted 24 h after the final irradiation. With the exception of mice irradiated for only 2 days, LC were significantly reduced throughout the chronic irradiation protocol, and no recovery occurred. DC numbers were significantly increased in the draining lymph nodes of mice irradiated for 20 days and 60 days.     

Solvothermal synthesis and structure of a new selenium-rich selenophosphate K(3)PSe(4).2Se(6)

The compound K(3)PSe(4).2Se(6) was synthesized at 110 degrees C via solventothermal techniques from binary starting materials and Se in acetonitrile. The compound crystallizes in the space group Fd macro 3 of the cubic system with eight formula units in a cell with a dimension of a = 16.415(2) A at T = 193 K. The structure contains an unusual intermixing of ionic and uncharged species. The selenophosphate tetrahedral trianions PSe(4)(3-) are surrounded by potassium cations; other potassium cations in the structure are coordinated to 12 selenium atoms from four Se(6) rings in a tetrahedral arrangement. There are no short contacts between adjacent selenium rings. Heating the same reaction mixture to 160 degrees C results in the formation of only needles of trigonal selenium.     

Zur Chemie derMeldrums?ure, 3. Mitt. Synthesen von Heterocyclen, 188. Mitt.

Thermolysis ofMeldrum acid in the presence of cycloalkanones leads to dioxaspiro-alkanediones (3 a–c) by the elimination of acetone. With increasing temperature an additional dehydratation is observed and with two moles ofMeldrum acid pyrano-cycloalkano-pyranediones (6 a–b) are formed. The reaction of dialkylMeldrum acids with cyclic 1,3-diones is investigated.     

Dynamic kinetic resolution of racemic tropic acid ethyl ester and its derivatives

The dynamic kinetic resolution of racemic mixtures of tropic acid ethyl ester under substrate racemizing conditions was studied using lipase PS with a ruthenium catalyst. Isopropenyl acetate was used as an acyl donor, since it was found to be compatible with both catalysts; this resulted in an efficient dynamic kinetic resolution. With this process, a variety of racemic tropic acid ethyl esters were transformed to optically active acetoxy-2-arylpropionic acid ethyl esters with 60-88% yields and 53-92% ee.     

Über den Nachweis von Palladium mit Violursäure

Zusammenfassung Eine Fällungsreaktion von Palladiumsalz mit Violursäure in saurer Lösung wird als Nachweismöglichkeit für das Element neben Platin, Rhodium und Gold herangezogen. Die Untersuchung der Palladiumverbindung zeigt, daß das Metall mit zwei Violursäureresten verknüpft ist.

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Summary A precipitation reaction of palladium salt with violuric acid in acid solution is used to detect this element in the presence of platinum, rhodium, and gold. The study of the palladium compound showed that the metal is bound to two violuric acid radicals.

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Résumé Mise en évidence de la possibilité d'identifier le palladium en solution acide, en présence de platine, de rhodium et d'or par une réaction de précipitation du sel de palladium par l'acide violurique. L'étude de la combinaison palladiée montre que le métal est lié à deux restes violuriques.

     

Synthesen von Heterocyclen, 121. Mitt.: Chinolizine und Indolizine V: Eine Synthese von 4-Methyl-2-chinolizinonen

Zusammenfassung Die Reaktion von 2-Pyridylessigsäurederivaten (1a, 1b) mit Diketen (2) in sied. Eisessig liefert in 1-Stellung substit. 4-Methyl-2-chinolizinone.

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Syntheses of heterocycles, CXXI: Quinolizines and indolizines. A synthesis of 4-methyl-2-quinolizinones

The reaction of 2-pyridylacetic acid derivatives (1a, 1b) with diketene (2), gives 4-methyl-2-quinolizinones.

     

FREQUENCY OF ULTRAVIOLET RADIATION-INDUCED MUTATION AT THE hprt LOCUS IN REPAIR-PROFICIENT MURINE FIBROBLASTS TRANSFECTED WITH THE denV GENE OF BACTERIOPHAGE T4

Abstract— Thc frequency of spontaneous and ultraviolet radiation (UVR)-induced mutation at the hprt locus was determined in control and denV-transfected, repair-proficient murine fibroblasts. Control cells removed an average of 25% of pyrimidine dimers induced by exposure to 150 J/m²UVR from an FS40 sunlamp within 24 h; under the same conditions of induction and repair, denV-transfected cells removed an average of 71% of pyrimidine dimers. Control cells were somewhat more resistant than denV-transfected cells to killing by UVR. The average frequency of spontancous mutation at the hprt locus for control and denV-transfected cells was 3 and 15 6-thioguanine (6-TG)-resistant colonies per 10⁶ surviving cells, respectively; there was no statistically significant difference between control and dcnV-transfected cells. However, after exposure to 75 or 150 J/m² UVR, denV-transfected cells had a significantly lower frequency of mutation to 6-TG resistance. After exposure to a fluence of 75 J/m², the average frequency of UVR-induced mutation at the hprt locus was 166 mutant colonies per lo^h surviving cells for control cells and 92 mutant colonies for denV-transfectcd cells; after 150 J/m², control cells had 205 6-TG-resistant colonies per 10⁶ cells, while dmV-transfected cclls had 61 mutant colonies. These results demonstrate that UVR-induced pyrimidine dimers are mutagenic photoproducts in mammalian cells.