Effect of H2S-uptake on the conversion of cyclohexene on Ru- and Pd-promoted molybdena-alumina catalysts

The effect of H₂S on the activity and selectivity of catalysts (Ru/Al₂O₃, Pd/Al₂O₃ and Ru and Pd promoted molydena-alumina) was different (on differnt catalysts and different conversions of cyclohexene). Ru-containing catalysts showed higher sulfur sensitivities than the Pd-containing ones. The sequence of catalysts by their H₂S uptake related to mass of catalyst was PdMo/Al₂O₃RuMo/Al₂O₃Mo/Al₂O₃>Pd/Al₂O₃Ru/Al₂O₃.     

Evidence of steric factors in the fungitoxic mechanisms of 8-quinolinol and its 2-, 3-, 4-, 5-, 6-and 7-chloro and bromo analogues

Summary A study was made of the fungitoxicity of 2-, 3-, 4-, 5-, 6- and 7-chloro and bromo-8-quinolinols againstAspergillus niger,A. oryzae,Myrothecium verrucaria,Trichoderma viride andTrichophyton mentagrophytes in Sabouraud dextrose broth and in Yeast Nitrogen Base supplemented with 1%D-glucose and 0.088%L-asparagine. Based on the presence or absence of synergism between pairs of substituted 8-quinolinols and reversal or nonreversal of toxicity byL-cysteine or N-acetyl-L-cysteine, the following conclusions were reached: (1) substituents on the quinoline ring change the site(s) of action of the toxicant; (2) the sites of action of the 5-, 6-, and 7-chloro-8-quinolinols are different from each other and from 8-quinolinol and its 2-, 3-, and 4-chloro analogues, and the same is true for the corresponding bromo compounds; (3) 8-quinolinol and its 3- and 4-chloro and bromo analogues appear to share common sites of action; (4) for good antifungal activity the 2 position of the ring must not be substituted by sterically bulky groups; (5) the geometry of the binding sites of action are not so constrained that they cannot accommodate the analogously substituted chloro- and bromo-8-quinolinols.

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Nachweis sterischer Faktoren bei der Fungitoxizität von 8-Chinolinol und seinen 2-, 3-, 4-, 5-, 6- und 7-Chlor- und -Brom-Analogen

Zusammenfassung Es wurde eine Studie der Fungitoxizität von 2-, 3-, 4-, 5-, 6- und 7-Chlor- und-Brom-8-chinolinol gegenüberAspergillus niger,A. oryzae,Myrothecium verrucaria,Trichoderma viride undTrichphyton mentagrophytes in Sabouraud Dextrose Nährmedium und in Hefe-N-Base mit 1%D-Glucose und 0.088%L-Asparagin unternommen. Auf der Basis des Zutreffens oder der Abwesenheit eines Synergismus zwischen Paaren von substituierten 8-Chinolinolen und der Umkehrung oder Nichtumkehrung der Toxizität durchL-Cystein oder N-Acetyl-L-cystein wurden folgende Schlußfolgerungen abgeleitet: (1) Substituenten am Chinolin-Ring ändern die Aktionsstelle(n) des Toxikans; (2) Die Angriffsstellen der 5-, 6- und 7-Chlor-8-chinolinole sind untereinander und von 8-Chinolinol und seinen 2-, 3- und 4-Chlor-Analogen verschieden, wobei das auch für die entsprechenden Brom-Verbindungen gilt; (3) 8-Chinolinol und seine 3- und 4-Chlor- und -Brom-Analogen scheinen gemeinsame Aktionsstellen zu teilen; (4) für eine gute antifungale Aktivität darf die 2-Position des Rings nicht mit sterisch anspruchsvollen Gruppen besetzt sein; (5) Die Geometrie des Bindungsstellen der Wirkung ist nicht so gespannt, daß nicht sowohl analoge Chlor- oder Brom-8-chinolinole Platz finden.

     

Theoretical rotational-vibrational spectra of theX 3 B 1,a 1 A 1 andb 1 B 1 states of NH 2 +

Summary The three-dimensional potential energy functions have been calculated from highly correlated multireference configuration interaction electronic wavefunctions for theX ³ B ₁,a ¹ A ₁, andb ¹ B ₁ states of the NH ₂ ⁺ ion. For the quasi-linear electronic ground state this information and the electric dipole moment functions have been used to calculate spectroscopic constants, line intensities and rotationally resolved absorption spectra. For thea ¹ A ₁-b ¹ B ₁ bent/quasi-linear Renner-Teller system ro-vibronic energy levels have been obtained from a variational approach accounting for anharmonicity, rotation-vibration and electronic angular momenta coupling effects. The vibronic levels are given for energies up to 13 500 cm^–1 for the bending levels and up to 8000 cm^–1 for the stretching and combination levels.Dedicated in the honor of Prof. Werner Kutzelnigg     

Glykosylazide als Ausgangsbasis zur Gewinnung von Nucleosidanalogen, 3. Mitt. Synthese von Alkylaminotetrazol- und Uretidinonnucleosiden

The -ribofuranosylazide1 is transformed after usual derivatization by suitable protecting groups into the P–N-ylid2, which gives the corresponding N-Glykosyl-N-alkylcarbodiimides4 and a small amount of the glykosylisocyanatde-rivative3 by reaction with alkylisocyanates. The carbodiimides4 were reacted with hydrazoic acid to give the alkylaminotetrazolnucleosides5 and finally the free nucleosidanalogs6. In the case of5 c the 5-aziridinyltetrazolnucleosid5 h was formed by an usual neighbouring group reaction. In addition the compound1 is transformed into the 3,5-diprotected anchor derivative7 by reaction withTIPSCl₂. The latter could be transformed by usual steps into the alkylaminotetra-zolnucleosides8 with a free 2-OH group. In the next step the 2-p-tolylthiocarbo-nates9 were prepared followed by transformation to the 2-desoxynucleosides10 by means of tributyltinhydride. Finally the free 2-desoxynucleosides11 were prepared. By reacting the carbodiimides4 with phenylisocyanate a mixture of the two possible regiouretidinonnucleosidderivatives12 and13 are formed. In the case of the N-glykosyl-N-allylcarbodiimide4 d only the one isomer13 d arises.

Herrn Prof. Dr.A. Neckel mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Dispersion state of CuO on CeO2

XRD and XPS are used to study the dispersion state of CuO on ceria surface. The dispersion capacity values of CuO measured by the two methods are consistent, which are of 1.20 mmol CuO/100 m² CeO₂. In addition, the results reveal that highly dispersed Cu²⁺ ions are formed at low CuO loadings and that increasing the CuO content to a value higher than its dispersion capacity produces crystalline CuO after the surface vacant sites on CeO₂ are filled. The atomic composition of the outermost layer of the CuO/CeO₂ samples has been probed by using static secondary ion mass spectroscopy (SSIMS), and the ratim of Cu/Ce are found to be 0.93 and 0.46 for the 1.22 and 0.61 mmol CuO/CeO₂ samples respectively. Temperature-programmed reduction (TPR) profile with two reduction peaks at 156 and 165°C suggests that the reduction of highly dispersed Cu²⁺ ions consists of two steps and is easier than that of CuO crystallites, in which the TPR profile has only one reduction peak at about 249°C. The above experimental results are in good agreement with the prediction of the incorporation model. Project supported by the National Natural Science Foundation of China.     

Multiple bonds between main group elements and transition metals, 155. (Hexamethylphosphoramide) methyl(oxo) bis(η-peroxo)rhenium(VII), the first example of an anhydrous rhenium peroxo complex: crystal structure and catalytic properties

Methyl(oxo)bis(η²-peroxo)rhenium(VII)1, the active species of the system CH₃ReO₃/H₂O₂ in the catalytic oxidation of different organic and organometallic compounds, is stabilized by a water molecule attached to the rhenium center. This water molecule can be removed and substituted by hexamethylphosphoramide (HMPA) to yield (hexamethylphosphoramide)methyl(oxo)bis(η²-peroxo rhenium(VII) (3). The synthesis, crystal structure (X-ray difraction study), and catalytic properties of which compound are reported. Crystal data are as follows: monoclinic, space group P2₁/n, A = 900.76(7) pm, B = 1229.80(11) pm, C = 1318.57(11) pm, β = 90.251(7)°, R_w = 0.034 for 1878 reflections. The catalytic properties of compound 3 in the oxidation of olefins with H₂O₂ are similar to those of 1.     

Magnetic microcapsules for targeted delivery of anticancer drugs

To achieve targeted distribution of anticancer drugs with sustained activity, ferromagnetic ethylcellulose microcapsules containing an anticancer drug, mitomycin C (FM-MMC-mc), were prepared by a method based on phase separation principles. Two prototypes of FM-MMC-mc were made: one with the drug as the core and zinc ferrite on its capsular surface (outer type); the other with both the drug and zinc ferrite as the core (inner type). Both preparations provided a sustained-release property and a sensitive response to conventional magnetic force, although certain differences in the release rate of drug, magnetic responsiveness, and particle size were found between the two dosage forms. Animal studies showed that the magnetic microcapsules could be magnetically controlled in the artery and urinary bladder. VX2 tumors in the rabbit hind limb and urinary bladder were successfully treated with magnetic control of FM-MMC-mc. Pharmacokinetic study revealed that the targeting of the microcapsules markedly enhanced the drug absorption into the surrounding tissues for a prolonged period of time. The results indicate the feasibility and effectiveness of the magnetic microcapsules as a targeted drug delivery system.     

Electrochemical vapor generation of selenium species after online photolysis and reduction by UV-irradiation under nano TiO<Subscript>2</Subscript> photocatalysis and its application to selenium speciation by HPLC coupled with atomic fluorescence spectrometry

An online UV photolysis and UV/TiO₂ photocatalysis reduction device (UV–UV/TiO₂ PCRD) and an electrochemical vapor generation (ECVG) cell have been used for the first time as an interface between high-performance liquid chromatography (HPLC) and atomic fluorescence spectrometry (AFS) for selenium speciation. The newly designed ECVG cell of approximately 115 L dead volume consists of a carbon fiber cathode and a platinum loop anode; the atomic hydrogen generated on the cathode was used to reduce selenium to vapor species for AFS determination. The noise was greatly reduced compared with that obtained by use of the UV–UV/TiO₂ PCRD–KBH₄–acid interface. The detection limits obtained for seleno-DL-cystine (SeCys), selenite (Se^IV), seleno-DL-methionine (SeMet), and selenate (Se^VI) were 2.1, 2.9, 4.3, and 3.5 ng mL^–1, respectively. The proposed method was successfully applied to the speciation of selenium in water-soluble extracts of garlic shoots cultured with different selenium species. The results obtained suggested that UV–UV/TiO₂ PCRD–ECVG should be an effective interface between HPLC and AFS for the speciation of elements amenable to vapor generation, and is superior to methods involving KBH₄.     

Regioselective cleavage of the bis-benzylidene acetal of d-mannitol under oxidative and reductive conditions: a new approach to C2-symmetric chiral ligands

A highly regioselective oxidative cleavage of 1,3:4,6-di-O-benzylidene-d-mannitol was carried out using NBS and the resultant product was readily converted to the C₂-symmetric chiral ligand, (R,R)-3,4-dihydroxy-1,5-hexadiene. On the other hand, reductive cleavage of 1,3:4,6-di-O-benzylidene-d-mannitol was achieved in a highly regioselective manner using BF₃·OEt₂ and Et₃SiH to give a highly functionalized benzyl ether, which was converted to a synthetically useful C₂-symmetric bis-amino alcohol derivative.