Highly diastereoselective synthesis of 11β,17β-diaryl-18a-homo-19-nor steroids

In a highly diastereoselective fashion novel 11β, 17β-diaryl steroids 17 and 18 were synthesized via Birch-type reduction [1] of styrylic precursors 11 and 15 . Both precursors were readily available by Suzuki-type coupling reactions [2] of aromatic boronic acids [3] and the corresoponding enol triflates 6, 10 , and 14 . Regioselective 17-enol triflate formation in presence of a 11-keto function could be demonstrated in case of steroid 5 . The remarkably high degree of stereo-selectivity observed parallels results from the natural series [4] and demonstrated a broader applicability of such single electron transfer reductions in stereoselective transformations on the steroid skeleton.     

Investigations on physical refining of animal fats and vegetable oils

Alcohols, polyethyleneglycols, supercritical fluids, and some of their mixtures have been investigated as to their usefulness to purify animal fats and vegetable oils by extraction. The main impurities are free fatty acids. Phase equilibrium was measured as function of temperature and pressure. As primary substances abattoir fat and palm oil were used. Carbon dioxide, dimethylether, and mixtures thereof, likewise methanol and ethanol were tested as extractants for free fatty acids by counter-current extraction in a pilot plant including a high-pressure column and by cross-flow extraction on laboratory scale. With experiments and process simulations including the recovery of the extractants the deacidification of animal fats and vegetable oils was found to be possible. Polyethyleneglycols extract carotenes together with free fatty acids. With the physical refining methods investigated, the formation of waste materials was avoided.     

Myristic Acid Inhibits the Activity of the Bacterial ABC Transporter BmrA

ATP-binding cassette (ABC) transporters are conserved in all kingdoms of life, where they transport substrates against a concentration gradient across membranes. Some ABC transporters are known to cause multidrug resistances in humans and are able to transport chemotherapeutics across cellular membranes. Similarly, BmrA, the ABC transporter of Bacillus subtilis, is involved in excretion of certain antibiotics out of bacterial cells. Screening of extract libraries isolated from fungi revealed that the C14 fatty acid myristic acid has an inhibitory effect on the BmrA ATPase as well as the transport activity. Thus, a natural membrane constituent inhibits the BmrA activity, a finding with physiological consequences as to the activity and regulation of ABC transporter activities in biological membranes.     

Alcoholysis of triacylglycerols by heterogeneous catalysis

Synthesis of fatty acid esters by alcoholysis, especially methanolysis of triacylglycerols was investigated using metal salts of amino acids as catalysts. The methanol to oil molar ratio was 6:1. It could be shown that salts containing a quaternary amino or a highly basic group as e.g. a guanidino group have catalytic activity in alcoholysis. Some of these salts are insoluble in monovalent alcohols, glycerol, and fatty acids esters and are therefore suitable catalysts for heterogeneously catalysed alcoholysis. Zinc salts of arginine, carnitine or histidine are among others suited for industrial use. These catalysts are also suitable for heterogeneously catalysed interesterification.     

Proteolytic Profiling of Streptococcal Pyrogenic Exotoxin B (SpeB) by Complementary HPLC-MS Approaches

Streptococcal pyrogenic exotoxin B (SpeB) is a cysteine protease expressed during group A streptococcal infection that represents a major virulence factor. Although subject to several studies, its role during infection is still under debate, and its proteolytic properties remain insufficiently characterized. Here, we revisited this protease through a set of complementary approaches relying on state of-the-art HPLC-MS methods. After conceiving an efficient protocol to recombinantly express SpeB, the zymogen of the protease and its activation were characterized. Employing proteome-derived peptide libraries, a strong preference for hydrophobic and aromatic residues at P2 alongside negatively charged amino acids at P3′ to P6′ was revealed. To identify relevant in vivo substrates, native proteins were obtained from monocytic secretome and plasma to assess their cleavage under physiological conditions. Besides corroborating our findings concerning specificity, more than 200 cleaved proteins were identified, including proteins of the extracellular matrix, proteins of the immune system, and proteins involved in inflammation. Finally, the cleavage of IgG subclasses was studied in detail. This study precisely depicts the proteolytic properties of SpeB and provides a library of potential host substrates, including their exact cleavage positions, as a valuable source for further research to unravel the role of SpeB during streptococcal infection.     

Beitrag zum enzymatischen Abbau von Stärkeschlichten auf einem Textilgut

Contribution to the Enzymatic Degradation of Starch Sizing Agents on a Textile Fabric. In this work some experiments concerning the enzymatic desizing of cotton fabrics using cyclodextrin glucosyl transferase are discussed. It has been reported that the enzyme catalyzes the formation of β-cyclodextrin in solution. The results demonstrate that it is possible to degrade starch on a textile fabric by means of CGTase. On the present conditions the enzyme catalyzes the formation of α-cyclodextrin. More experimental work is necessary to optimize the conditions for enriching β-cyclodextrin against α-cyclodextrin.     

Novel solution route synthesis of low thermal conductivity nanocrystalline bismuth telluride

A novel synthesis approach based on a solution route has been developed for the fabrication of nanocrystalline bismuth telluride. The method consists of dissolving both bismuth and tellurium into the same organic solvent with the assistance of complexing agents and one-step coprecipitation of bismuth telluride. The synthesized nanocrystalline bismuth telluride powders possess rhombohedral crystal structure and are nanosheet/nanorod-like with an average size of between 30 and 40 nm. The thermal conductivity of the hot-pressed compact consolidated from the as-synthesized nanopowders is 0.39-0.45 Wm(-1)K(-1) in the temperature range of 323 to 523 K, which is at most one third of that of bulk bismuth telluride-based materials reported in the literature. Such low thermal conductivity of the investigated bismuth telluride is mainly attributed to substantially high concentration of grain boundaries provided by nanostructuring to scatter phonons intensively.     

Location Planning for the Production of CO2-Based Chemicals Using the Example of Olefin Production

A methodology for identifying suitable locations for the CO₂-based production of olefins in Germany is presented. Based on electricity and CO₂ requirements, locations are identified that can provide sufficient CO₂ and renewable energy for the conversion of CO₂ to olefins. In addition, the use of existing infrastructures is taken into account. The regional, technical renewable energy potential in Germany is sufficient to produce ∼ 800 kt of olefins from CO₂-based methanol per year in one plant. But the currently available CO₂ point sources with high CO₂ concentrations of around 100 % are not sufficient to meet the CO₂ requirement of an 800 kt a⁻¹ methanol-to-olefins plant. If existing refineries are preferred due to existing infrastructure services, locations in the north of Cologne, in Lower Saxony, and in Brandenburg are particularly suitable. A full substitution of fossil olefins by CO₂-based olefins is possible in Germany. The challenge is to provide sufficient renewable electricity for the production of H₂ with a low CO₂ intensity.     

Synthesis of Tetramic Acid Fragments Derived from Vancoresmycin Showing Inhibitory Effects towards S. aureus

An efficient route to various vancoresmycin-type tetramic acids has been developed. The modular route is based on an effective Fries-type rearrangement to introduce various appending acetyl residues. The minimum inhibitory concentration (MIC) values of the new tetramic acids against Staphylococcus aureus and Escherichia coli were determined, revealing that three of the new compounds exhibit antimicrobial activity against S. aureus. These bioactive compounds were structurally most closely related to the authentic vancoresmycin building block. Additionally, the compounds induced a lial-lux bioreporter, which responds to cell wall stress induced by antibiotics that interfere with the lipid II biosynthesis cycle. These data suggest the tetramic acid moiety to be a part of the vancoresmycin pharmacophore.