Über 1,2-Umlagerungen und C?H-Einschubreaktionen Acyclischer Alkylidencarbene

On 1.2-Shift Reactions and C H-Insertions of Acyclic Alkylidene Carbenes Two series of acyclic terminal vinyl bromides ( 1 … 4 and 5 … 7 ) were tested in the reaction with potassium tert-butoxide as precursors of alkylidene carbenes. As expected 1 up to 4 only give 1-alkynes whereas the 2-methylated vinyl bromides 5 , 6 and 7 yield 1-methylated cyclopentenes predominantly besides 2-alkynes. The formation of cyclopentenes indicates a reaction route via alkylidene carbenes and 1,5-C H-insertion reactions, that of 2-alkynes is convincing evidence for 1,2-alkyl shift reactions in 2-methyl substituted alkylidene carbenes. The selectivity of 1,5-C H-insertion depends on the degree of alkyl substitution of the C-5-atom. At 240°C the selectivity is 1°:2°:3° ≈ 1:54:240.     

Abwasser zu Prozesswasser – zwei unterschiedliche Ansätze

Wastewater reuse and recycling will play an increasingly important role in solving future water stress worldwide. Water of high quality and purity is an indispensable raw material for industry in many production steps, so the availability of water is a decisive location factor for industry. Innovative concepts for wastewater reuse and recycling within the framework of operator models based on many years of know-how lead to the conservation of scarce water resources and to a sustainable and financially attractive water supply. As the presented reference plants show, ecologically and economically advantageous solutions can be created for municipalities, industry, and water suppliers.     

Über die strukturanalystische Anwendung von „anomalen”︁ Multipletts in off-resonance entkoppelten 13C-NMR-Spektren von ?CH  CH?Fragmenten

On the Structural Analytical Application of „Anomalous”︁ Multiplets in Off-resonance Decoupled ¹³C NMR Spectra of  CH  CH Fragments The theoretical background of “anomalous” splitting of signals of molcular fragments  CHCH in off-resonance decoupled ¹³C NMR spectra is described. The use of these splitting phenomena on the determination of vicinal H,H and geminal C,H coupling constants is demonstrated using simple examples. The possibilities to determine the configuration of double bonds are shown by other examples from the field of natural constituents chemistry.     

Parkinson’s Disease: A Prionopathy?

The principal pathogenic event in Parkinson’s disease is characterized by the conformational change of α-synuclein, which form pathological aggregates of misfolded proteins, and then accumulate in intraneuronal inclusions causing dopaminergic neuronal loss in specific brain regions. Over the last few years, a revolutionary theory has correlated Parkinson’s disease and other neurological disorders with a shared mechanism, which determines α-synuclein aggregates and progresses in the host in a prion-like manner. In this review, the main characteristics shared between α-synuclein and prion protein are compared and the cofactors that influence the remodeling of native protein structures and pathogenetic mechanisms underlying neurodegeneration are discussed.     

Über die Si?N-Bindung. XXXIX [1]. Kinetische Untersuchungen zur spontanen Hydrolyse,Alkoholyse und Phenolyse von Aminosilanen

Silicon-Nitrogen Bonds. XXXIX. Kinetic Studies on the Spontaneous Hydrolysis, Alcoholysis, and Phenolysis of Silylamines It could be shown by polarimetric and DC-metric methods that hydrolysis, alcoholysis, and phenolysis of silylamines are of second order and lead to equilibria. The rate of equilibrium establishment is determined by the position of a preceding protonation equilibrium and by steric effects. The position of the equilibria depends on inductive and steric effects. The enthalpy of activation for the ethanolysis of Me₃SiNHPh was determined to 27,2 kJ/mol and the entropy of activation to –231 J/K · mol. The mechanism of the reactions is given.     

Säurekatalysierte Umsetzungen von Aromaten mit Alkanen und Cycloalkanen. VI. Alkylierungen mit niederen Alkanen (C3?C5)

Acid-catalyzed Reactions of Aromatic Hydrocarbons with Alkanes and Cycloalkanes. VI. Alkylations with Lower Alkanes (C₃ C₅) Benzene and toluene are alkylated in the presence of HF/SbF₅, CF₃SO₃H/SbF₅, HBr/AlBr₃ or CF₃SO₃H/AlBr₃ by propane, n- and isobutane or n- and isopentane to products of complex composition, using a special apparature where the gases are circulated. The results of these experiments are compared with corresponding results in an autoclave. The reaction products of benzene with isobutane were analyzed, qualitatively and quantitatively, by gas-liquid chromatography and mass spectrometry.     

In‐situ‐EPR‐Spektroskopie in der heterogenen Katalyse: Stiefkind oder Lichtblick?

This review evaluates the potential of electron paramagnetic resonance (EPR, also known as electron spin resonance, ESR) as an in situ technique for analyzing structure‐reactivity relationships in heterogeneous catalysis under reaction condition. It starts with a general overview on the state of the art, followed by a short introduction of its theory. In due course the use of the method is illustrated by three selected application examples. At the end a critical evaluation of opportunities and limitations of in situ EPR in heterogeneous catalysis is given.     

iso‐OPDA: An Early Precursor of cis‐Jasmone in Plants?

Cis-jasmone is a highly appreciated fragrance and plant-derived signal molecule that controls pollination, attracts parasitoids of attacking herbivores, and serves as an intra- and interspecific signal that controls gene expression. cis-Jasmone is produced from linolenic acid along the jasmonic acid cascade. In addition to the conversion of jasmonic acid into cis-jasmone, a novel pathway might exist that converts cis-oxophytodienoic acid (OPDA), an early precursor of jasmonic acid, into iso-OPDA. The planar iso-OPDA is degraded by beta-oxidation to 3,7-didehydrojasmonic acid, which yields cis-jasmone by spontaneous decarboxylation. The degradation of iso-OPDA to cis-jasmone is demonstrated for many plant species and the yeast Saccharomyces cerevisiae.     

La 1?x Ca x MnO3 semiconducting nanostructures: morphology and thermoelectric properties

Semiconducting metallic oxides, especially perosvkite materials, are great candidates for thermoelectric applications due to several advantages over traditionally metallic alloys such as low production costs and high chemical stability at high temperatures. Nanostructuration can be the key to develop highly efficient thermoelectric materials. In this work, La _1−xCa_xMnO₃ perosvkite nanostructures with Ca as a dopant have been synthesized by the hydrothermal method to be used in thermoelectric applications at room temperature. Several heat treatments have been made in all samples, leading to a change in their morphology and thermoelectric properties. The best thermoelectric efficiency has been obtained for a Ca content of x=0.5. The electrical conductivity and Seebeck coefficient are strongly related to the calcium content.     

Natural Dibenzo-α-Pyrones: Friends or Foes?

Natural dibenzo-α-pyrones (DAPs) can be viewed from two opposite angles. From one angle, the gastrointestinal metabolites urolithins are regarded as beneficial, while from the other, the emerging mycotoxin alternariol and related fungal metabolites are evaluated critically with regards to potential hazardous effects. Thus, the important question is: can the structural characteristics of DAP subgroups be held responsible for distinct bioactivity patterns? If not, certain toxicological and/or pharmacological aspects of natural DAPs might yet await elucidation. Thus, this review focuses on comparing published data on the two groups of natural DAPs regarding both adverse and beneficial effects on human health. Literature on genotoxic, estrogenic, endocrine-disruptive effects, as well as on the induction of the cellular anti-oxidative defense system, anti-inflammatory properties, the inhibition of kinases, the activation of mitophagy and the induction of autophagy, is gathered and critically reviewed. Indeed, comparing published data suggests similar bioactivity profiles of alternariol and urolithin A. Thus, the current stratification into hazardous Alternaria toxins and healthy urolithins seems debatable. An extrapolation of bioactivities to the other DAP sub-class could serve as a promising base for further research. Conclusively, urolithins should be further evaluated toward high-dose toxicity, while alternariol derivatives could be promising chemicals for the development of therapeutics.     

The trans‐10,cis‐15 18:2: a Missing Intermediate of trans‐10 Shifted Rumen Biohydrogenation Pathway?

The “trans-10 shifted” biohydrogenation pathway is frequently established in the rumen when high starch diets are fed to ruminants, resulting in the accumulation of trans-10 18:1 in ruminant products. It has been proposed that the “trans-10 shifted” biohydrogenation pathway of α-linolenic acid generates two intermediates, the trans-10,cis-15 18:2 and trans-10,cis-12,cis-15 18:3, although none of these have been found in the rumen. We analyzed digestive contents and meat samples from two trials, where animals were fed: a compound feed diet supplemented with 8 % oil blend containing linseed oil (samples A); and a forage based diet supplemented with 6 % linseed oil (samples B). The use of the new SLB-IL111 chromatographic column allowed the detection of two different 18:2 isomers in each sample trial, which could not be resolved when the CP-Sil 88 column is used. The two 18:2 isomers were characterized by mass spectrometry using 4,4-dimethyloxazoline derivatives. However, because they were subject to higher temperatures and present different chromatographic properties compared with the fatty acid methyl esters, we also used the “covalent adduct chemical ionization” technique to confirm the identity of both 18:2 isomers. We detected and identified the 10,15-18:2 in samples A and the 11,15-18:2 in samples B. The geometry of both isomers was tentatively assigned as trans,cis taking in account their elution order and biologic plausibility. As far as we know, this is the first time that the trans-10,cis-15 18:2 has been found in ruminant digestive contents and meat samples associated with the “trans-10 shifted” biohydrogenation pathway of α-linolenic acid.     

Edible Bioactive Film with Curcumin: A Potential “Functional” Packaging?

Edible packaging has been developed as a biodegradable and non-toxic alternative to traditional petroleum-based food packaging. Biopolymeric edible films, in addition to their passive protective function, may also play a bioactive role as vehicles for bioactive compounds of importance to human health. In recent years, a new generation of edible food packaging has been developed to incorporate ingredients with functional potential that have beneficial effects on consumer health. Curcumin, a bioactive compound widely used as a natural dye obtained from turmeric rhizomes (Curcuma longa L.), has a broad spectrum of beneficial properties for human health, such as anti-inflammatory, anti-hypertensive, antioxidant, anti-cancer, and other activities. To demonstrate these properties, curcumin has been explored as a bioactive agent for the development of bioactive packaging, which can be referred to as functional packaging and used in food. The aim of this review was to describe the current and potential research on the development of functional-edible-films incorporating curcumin for applications such as food packaging.