Malonic ester derivatives of s-Triazine

Reaction of cyanuric chloride with solutions of sodium diethyl malonate led to three products, 2,4,6-tris(dicarbethoxymethylene)hexahydro-s-triazine, 2,4-bis(dicarbethoxymethylene)-6-oxohexahydro-s-triazine, and 2-dicarbethoxymethylene-4,6-dioxohexahydro-s-triazine. The preferred structures (IV,V,VI) are stabilized by chelated N-H-O protons in six membered rings. The assignment of structures was made on the basis of ir, nmr, uv and mass spectral data.     

Chemie der Pleuromutiline,VII. Basisch induzierte transanulare 1,4-Hydridverschiebung in 8-substituierten Pleuromutilinderivaten

The syntheses of the pleuromutilin derivatives12 and16 are described. Both compounds on treatment with base rearrange to the isomeric ketol13. The results of the deuteration experiment as well as the kinetic measurements are in agreement with the hypothesis of an intramolecular 1,4-hydride shift.

Die 3-Hydroxyverbindung4 ist nicht isolierbar.     

Purity assessment of crystalline zearalenone

Commercially available solid zearalenone (ZON) to be used as a certified liquid calibrant (BCR-699) in a project funded by the European Commission within the Standard Measurement and Testing program was characterized and its purity determined. The degree of purity of the ZON was examined by UV spectrophotometer, liquid chromatography (LC) with diode array and fluorescence detection, 1H and 13C-NMR spectrometry, LC-mass spectrometry (LC/MS/MS), ion chromatography (IC), and differential scanning calorimetry (DSC). The diagrams obtained from DSC analysis and the UV spectrum showed no detectable impurities. Likewise, no impurities were observed by LC analysis with both diode array and fluorescence detection. IC determination revealed negligible contamination of ZON with chloride of 0.020 +/- 0.005% and nitrate of 0.016 +/- 0.006%. Zearalanone (ZAN) was identified as one of 2 minor (0.2%) impurities by LC/MS/MS. The 1H-NMR measurements revealed an additional peak, which has not been previously reported in the literature. It could be identified as part of the ZON spectrum as the signal arising from the phenolic proton attached to C4'. The manufacturer states an additional contamination with 0.2% methylene chloride, which could be confirmed to an extent of 0.1% by 1H-NMR. Minor impurities, whose structures remain unknown, were discovered at 3.5 and < 1 ppm. Total percentage of impurities based on NMR measurement was estimated not to exceed 1%. A purity of 99.5% with a tolerance of +/- 0.5% was finally attributed to the ZON studied in this project.     

Chemie der Pleuromutiline, 11. Mitt.: Konfigurationsumkehr der Vinylgruppe am Kohlenstoff 12 durch reversible Retro-En-Spaltung

The reaction of pleuromutilin-22-0-tosylat(2) withEtZnI afforded a mixture of the 12-epimeric compounds2 and3. A reversible retro-en-reaction of the homoallylic system is discussed as a possible mechanistic pathway. The structure assignment is based on¹H- and¹³C-NMR spectroscopic data.

Für Verbindungen dieser Substanzklasse, die auf ihre antibakterielle Aktivität geprüft werden, ist erfahrungsgemäß eine basisch substituierte Acylgruppierung in Position 14 erforderlich⁴. Heterocyclische Acylgruppierungen erwiesen sich dabei als besonders wirkungsvoll.     

Chemie der pleuromutiline-VIII : Funktionalisierung des C-atoms 13 durch intramolekulare nitreninsertion. Synthese des 14-o-[(3-amino-1,2,4-triazol-5yl)thioacetyl]-13-amino-19,20- dihydromutilin-hydrochlorid

The acylazide 6, which is readily available from 19,20-dihydromutilin, is thermally decomposed to give the appropriate nitrene. Despite the proximity to the methyl group at C-9 this nitrene inserts regio-and stereospecifically into the C-13-βH bond. The resulting cyclic carbamate 7 is converted in several steps into the formylated amine 11. After introduction of the hererocyclic substituent which was chosen for biological reasons,^15,16 followed by a hydride shift,¹² the title compound 16 is obtained.     

Solid phase extraction for the determination of ibuprofen by means of HPLC and UV detection in the lower ng range in plasma and urine

Summary Ibuprofen in the lower ng range could, up to now, only be determined in biological samples by means of specific detectors. In the following a time-saving HPLC method with UV detection after solid phase extraction is described. The lower detection limit is 0.5 ng/20 l of sample volume. The linear range is between 0 and 10.0 ng of ibuprofen per injection. The mean standard deviation and mean coefficient of variation are 0.12 ng and 2.6%. The selectivity of the method is assured.     

Electronic and structural studies of immobilized thiol-derivatized cobalt porphyrins on gold surfaces

The immobilisation of thiol-derivatized cobalt porphyrins on gold surfaces has been studied in detail by means of combined scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). S-thioacetyl has been used as a protective group for the thiol. Different routes for deprotection of the acetyl groups were performed in acidic and in basic conditions. The results show the formation of monolayer films for the different preparation schemes. The immobilisation of the molecules on the gold surface takes place through the thiol-linkers by the formation of multiple thiolate bonds. In the case of layers formed with protected porphyrins approximately 60% of the linkers are bonded to the gold surface whereas for deprotected layers the amount of bonded linkers is increased up to about 80%. STM measurements revealed that the molecules arrange in a disordered overlayer and do not exhibit mobility on the gold surface. Annealing experiments have been performed in order to test the stability of the porphyrin layers. Disordered patterns have been observed in the STM images after annealing at T = 400 °C. XPS revealed that the sulphur content disappeared completely after annealing at T = 180 °C and that the molecules did undergo significant modifications.     

Remote preparation of an atomic quantum memory

Storage and distribution of quantum information are key elements of quantum information processing and future quantum communication networks. Here, using atom-photon entanglement as the main physical resource, we experimentally demonstrate the preparation of a distant atomic quantum memory. Applying a quantum teleportation protocol on a locally prepared state of a photonic qubit, we realized this so-called remote state preparation on a single, optically trapped 87Rb atom. We evaluated the performance of this scheme by the full tomography of the prepared atomic state, reaching an average fidelity of 82%.     

Bidirectional, organocatalytic synthesis of lepidopteran sex pheromones

Shuffling of two simple building blocks and a regioselective transfer hydrogenation allow for the rapid synthesis of a small collection of lepidopteran sex pheromones, e.g., 8E,10Z-tetradeca-8,10-dienal 5c, from the horse chestnut leafminer (Cameraria ohridella).