Kristallistrukturanalyse von lösungsmitterfreiem Lithium-benzoat. Relevanz föur die Material-eigenschaften von Lithium-carboxylaten?

Anhydrous Li benzoate crystallizes from water as very thin, soft, and flexible platelets. The poor quality of these crystals rendered the data collection for the crystal structure determination very difficult. Anisotropic refinement did not reduce the R value below 0.1. The Li benzoate molecules form a two-dimensional polymeric structure consisting of a grid of lithium and carboxylate O-atoms, with the Ph groups forming kind of a covering layer on each side. The polymeric layers are stacked with phenyl CH groups pointing towards each other. Thus, very weak van-der-Waals forces hold the layers together. This structural feature is in agreement with the macroscopic properties of the crystals and probably causes Li carboxylates to be valuable components of high-temperature, high-performance greases (for instance in the vacuum technology). The structures of Li benzoate and of other Li carboxylates may also provide a clue for the fact that ionomers containing LiOOC groups are especially tough materials

Grossansätze zur Herstellung von α,α,α',α'-Tetraaryl-1,3-dioxolan-4,5-dimethanolen (TADDOLe): Nützliche Hilfsstoffe für die EPC-Synthese und ihre Struktur im Festkörper

The large-scale preparation of α,α,α',α'-tetraaryl-1,3-dioxolan-4,5-dimethanol derivatives is described. It consists of acetalization of dimethyl tartrate and Grignard addition. The diols 2–12 thus obtained are crystalline and stable. They are useful as versatile auxiliaries for enantioselective reactions and for resolutions by clathrate formation. The X-ray crystal structure of the inclusion compound from one of the TADDOLs and CCl4 is described (6·2 CCl4) and compared with the structures of analogous derivatives, including C2-symmetrical diphosphines. Reference is given to other chiral auxiliaries containing the diaryl-methanol group

Oxidative Cleavage of α‑Aryl Aldehydes Using Iodosylbenzene

We found that α-aryl aldehydes can be cleaved to chain-shortened carbonyl compounds and formaldehyde by various iodosylbenzene complexes. A mechanistic scheme is presented that accounts for the loss of one carbon atom. Formaldehyde is further oxidized to CO and CO₂ under the reaction conditions

A combined gas-phase, solution-phase, and computational study of C−H activation by cationic iridium(III) complexes

A combination of electrospray ionization MS/MS techniques, isotopic labeling experiments in the gas-phase and solution, and ab initio calculations is used to study the C−H activation reactions of [Cp*Ir(PMe3)(CH3)]+ and [CpIr(PMe3)(CH3)]+. The reaction in the gas phase was found to proceed through a Cp or [Cp*Ir(η2-CH2PMe2)]+ intermediate. Quantitative collision-induced dissociation (CID) threshold measurements were used along with general models for ion−molecule reactions to construct potential energy diagrams which rationalize the gas-phase results. The comparison between the two complexes, and between the reactions in the gas phase and in solution, suggests that the reaction through the intermediacy of a metallaphosphacyclopropane could be favored over the conventional (and simpler) oxidative addition/reductive elimination mechanism when the Ir(III) complex is rendered more electron deficient

Katalytisch beschleunigte Gasphasenreaktionen

patent submitter:Chen, Peter, Zürich (CH)In a process for carrying out a reaction in the gaseous phase catalytically accelerated by anion or cations, the catalyst is introduced into the gaseous reaction mixture as a free anion or cation without the corresponding counter-ion, and at least substantially without solvent. The catalyst is activated in a solvent and then the solvent and the counter-ion are substantially removed before the catalyst is introduced into the reaction mixture. This process is particularly suitable for the production of polyolefins

Crystallization of a 45 kDa peroxygenase/peroxidase from the mushroom Agrocybe aegerita and structure determination by SAD utilizing only the haem iron

Some litter-decaying fungi secrete haem-thiolate peroxygenases that oxidize numerous organic compounds and therefore have a high potential for applications such as the detoxification of recalcitrant organic waste and chemical synthesis. Like P450 enzymes, they transfer oxygen functionalities to aromatic and aliphatic substrates. However, in contrast to this class of enzymes, they only require H2O2 for activity. Furthermore, they exhibit halogenation activity, as in the well characterized fungal chloroperoxidase, and display ether-cleavage activity. The major form of a highly glycosylated peroxygenase was produced from Agrocybe aegerita culture media, purified to apparent SDS homogeneity and crystallized under three different pH conditions. One crystal form containing two molecules per asymmetric unit was solved at 2.2 Å resolution by SAD using the anomalous signal of the haem iron. Subsequently, two other crystal forms with four molecules per asymmetric unit were determined at 2.3 and 2.6 Å resolution by molecular replacement

Metabolic and Lipidomic Assessment of Kidney Cells Exposed to Nephrotoxic Vancomycin Dosages

Vancomycin is a glycopeptide antibiotic used against multi-drug resistant gram-positive bacteria such as Staphylococcus aureus (MRSA). Although invaluable against resistant bacteria, vancomycin harbors adverse drug reactions including cytopenia, ototoxicity, as well as nephrotoxicity. Since nephrotoxicity is a rarely occurring side effect, its mechanism is incompletely understood. Only recently, the actual clinically relevant concentration the in kidneys of patients receiving vancomycin was investigated and were found to exceed plasma concentrations by far. We applied these clinically relevant vancomycin concentrations to murine and canine renal epithelial cell lines and assessed metabolic and lipidomic alterations by untargeted and targeted gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry analyses. Despite marked differences in the lipidome, both cell lines increased anabolic glucose reactions, resulting in higher sorbitol and lactate levels. To the best of our knowledge, this is the first endometabolic profiling of kidney cells exposed to clinically relevant vancomycin concentrations. The presented study will provide a valuable dataset to nephrotoxicity researchers and might add to unveiling the nephrotoxic mechanism of vancomycin