Die Struktur des Bisindolalkaloides Amatain ( = Grandifolin,Subsessilin)

The structure of the bisindole alkaloid amataine (= grandifoline, subsessiline) Amataine ( 1 ) was isolated from the roots of Hedranthera barteri (HOOK . F .) PICHON (Apocynaceae). In comparison to the alkaloid vobtusine ( 5 ), which was isolated from the same plant, 1 contains two hydrogen atoms less. By reduction of 1 with H₂/PtO₂ or with NaBH₄ dihydromataine ( = isovobtusine, 13 ) was formed which is isomeric to 5 . Acid catalysed water addition to 1 afforded hydratoamataine ( 15 ), which was reduced to 5 with NaBH₄. Thermolysis of 15 gave 1 . The difference between the two isomeric bases 5 and 13 has to be attributed to a different configuration at the spirocenter C(7). In contrast to 5 amataine ( 1 ) contains an ether bridge instead of a hydroxy group; this bridge is located between C (2′) and C (8).     

Copper Salt‐Controlled Divergent Reactivity of [Cu]CF2PO(OEt)2 with α‐Diazocarbonyl Derivatives

Herein, we report a copper salt‐controlled divergent reactivity toward α‐diazocarbonyl compounds. By a simple change of the copper counteranion under identical reaction conditions, the reported method allowed an easy access to either (Z)‐α‐fluorovinylphosphonate or alkyl‐SCF₂PO(OEt)₂ derivatives in good yields. Mechanistic studies were performed and suggested two different pathways to explain the formation of these products.     

Nucleation of Polypropylene Crystallization with Gold Nanoparticles. Part 2: Relation between Particle Morphology and Nucleation Activity

The influence of gold nanoparticle morphology on nucleation of isotactic polypropylene (PP) crystallization was investigated. Previous experiments indicated certain nucleation activity of gold nanoparticles, varying with their size. In this work, eight types of gold micro/nanoparticles were used: vacuum-sputtered nanostructures (nanoparticles, nanoislands, and nanolayers), chemically prepared isometric gold nanocrystals (5, 20, and 100 nm diameters), and two types of gold microcrystals with well-developed crystal facets [with (100) and (111) facets, respectively]. To minimize the effect of particle agglomeration, we used our recently introduced sandwich method, in which the nucleating agent was deposited between thin PP films and the nucleation was evaluated by polarized light microscopy (PLM), X-ray scattering (WAXS), and differential scanning calorimetry (DSC). The nucleation activity of Au particles in PP was lower than it might be expected from the previous studies and depended on their morphology. The nucleation activity of Au microcrystals with well-developed facets was higher than the activity of non-faceted Au nanocrystals.     

Nucleation of Polypropylene with Gold Nanoparticles. Part 1: Introduction of Sandwich Method for Evaluation of Very Weak Nucleation Activity

Although gold particles are known to nucleate isotactic polypropylene (PP), the nucleating effect of chemically pure 5 nm Au, prepared in vacuum sputter coater, was found to be hardly observable. In order to detect such a weak effect, we deposited a homogeneous layer of Au nanoparticles between thin PP films and evaluated the nucleation activity by a combination of three independent methods: polarized light microscopy (PLM), differential scanning calorimetry (DSC), and 2D wide-angle X-ray scattering (2D-WAXS). This new technique, which was called sandwich method, allowed us to demonstrate that gold nanoparticles were able to nucleate PP crystallization, although the effect was much weaker than that produced by commercial α-nucleant [1,2,3,4-bis(3,4-dimethylbenzylidene)sorbitol] and β-nucleant (N,N-Dicyclohexyl-2,6-naphthalene dicarboxamide). The sandwich method appeared to be quite universal and applicable for any micro-sized nucleants or nanonucleants.     

Elucidation of the decomposition pathways of protonated and deprotonated estrone ions: application to the identification of photolysis products

With the future aim of elucidating the unknown structures of estrogen degradation products, we characterized the dissociation pathways of protonated estrone (E1) under collisional activation in liquid chromatography/tandem mass spectrometry (LC/MS/MS) experiments employing a quadrupole time‐of‐flight mass spectrometer. Positive ion and negative ion modes give information on the protonated and deprotonated molecules and their product ions. The mass spectra of estrone methyl ether (CH₃‐E1) and estrone‐d₄ (E1‐d₄) were compared with that of E1 in order (i) to elucidate the dissociation mechanisms of protonated and deprotonated molecules and (ii) to propose likely structures for each product ions. The positive ion acquisition mode yielded more fragmentation. The mass spectra of E1 were compared with those of estradiol (E2), estriol (E3) and 17‐ethynylestradiol (EE2). This comparison allowed the identification of marker ions for each ring of the estrogenic structure. Accurate mass measurements have been carried out for all the identified ions. The resulting ions revealed to be useful for the characterization of structural modifications induced by photolysis on each ring of the estrone molecule. These results are very promising for the determination of new metabolites in the environment. Copyright © 2010 John Wiley & Sons, Ltd.     

Continuous electrochemical monitoring of nitric oxide production in murine macrophage cell line RAW 264.7

In this study, we realized the continual and long-term electrochemical detection of NO production by stimulated macrophages using modified porphyrinic microsensor. The NO release from RAW 264.7 cells stimulated by lipopolysaccharide started 5 h after the lipopolysaccharide administration. After reaching its maximum at the sixth hour, the stable level of NO production was observed between the seventh and 12th hour of the experiment. This phase was followed by a gradual decline in NO production. A close correlation between the NO signal detected with microelectrode and nitrite accumulation, which had been determined in supernatants removed from stimulated cells, was observed. This finding was utilized for the calibration of the electrochemical experiment. The presence of iNOS enzyme, which constitutes a main requirement for NO production by stimulated macrophages, was confirmed by Western blot analysis of iNOS protein expression at key time points of the corresponding electrochemical experiment. The capability of our microsensor to instantaneously monitor the changes in the NO production by stimulated RAW 264.7 cells was demonstrated by the immediate decrease in the signal due to NO as a response to the addition of iNOS inhibitor into the cell culture medium. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

State-Selected Unimolecular Decomposition of δ-Valerolactam(+) and δ-Valerolactam(2)(+) Cations: Theory and Experiment

The near threshold photofragmentation pattern of δ-valerolactam(+) and δ-valerolactam(2)(+) has been recorded combining electron/ion coincidence techniques and vacuum ultraviolet synchrotron radiation. The experimental method yields the fragment intensity as a function of the internal energy deposited into the parent cation, up to 3.1 eV above the first ionization threshold. In parallel, ab initio studies on the δ-valerolactam(+) and δ-valerolactam(2)(+) cations and their ionic and neutral fragmentation products have been performed with the aim of determining the isomers of the ionic products observed experimentally as well as of their neutral counterparts. These computations were performed using the PBE0 exchange-correlation functional and the aug-cc-pVDZ basis set. We found good agreement between the calculated reaction enthalpies and experimental appearance energies of the ions. More generally, our experimental and theoretical results reveal that the fragmentation of the ionic species of interest leads to a multitude of neutral and ionic fragments, which may be formed after intramolecular isomerization and complex decomposition processes. Multistep reaction pathways are expected.