Investigations for the detection of genotoxic substances on TLC plates

The present study describes modifications to an existing bioautographic method for detecting genotoxic substances on thin-layer chromatography (TLC) plates by using the umu assay. It will be shown that the complex procedure that is described in the literature can be significantly simplified. Using the modified method, it is possible to detect 0.3?ng of the genotoxic substance 4-nitroquinoline-N-oxide. With 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal), a suitable substrate for environmental samples for the detection of the resulting β-galactosidase was found. Experiments showed, in contrast, that indirectly genotoxic substances could not thus far be identified on the TLC plate with overlayer bioautography.     

Molecular Precursors for the Phase‐Change Material Germanium‐Antimony‐Telluride,Ge2Sb2Te5 (GST)

This review provides an overview of the precursor chemistry that has been developed around the phase‐change material germanium‐antimony‐telluride, Ge₂Sb₂Te₅ (GST). Thin films of GST can be deposited by employing either chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques. In both cases, the success of the layer deposition crucially depends on the proper choice of suitable molecular precursors. Previously reported processes mainly relied on simple alkoxides, alkyls, amides and halides of germanium, antimony, and tellurium. More sophisticated precursor design provided a number of promising new aziridinides and guanidinates.     

Rearrangement Reactions of Tritylcarbenes: Surprising Ring Expansion and Computational Investigation

As a rule, acetylides and sulfonyl azides do not undergo electrophilic azide transfer because 1,2,3‐triazoles are usually formed. We show now that treatment of tritylethyne with butyllithium followed by exposure to 2,4,6‐triisopropylbenzenesulfonyl azide leads to products that are easily explained through the generation of short‐lived tritylethynyl azide and its secondary product cyanotritylcarbene. Furthermore, it is demonstrated that tritylcarbenes generally do not produce triphenylethenes exclusively, as was stated in the literature. Instead, these carbenes always yielded also (diphenylmethylidene)cycloheptatrienes (heptafulvenes) as side products. This result is supported by static DFT, coupled cluster, and ab initio molecular dynamics calculations. From these investigations, the fused bicyclobutane intermediate was found to be essential for heptafulvene formation. Although the bicyclobutane is also capable of rearranging to the triphenylethene product, only the heptafulvene pathway is reasonable from the energetics. The ethene is formed straight from cyanotritylcarbene.     

Two Pseudopolymorphic Star‐Shaped Tetranuclear Co3+ Compounds with Disulfide Anions Exhibiting Two Different Connection Modes and Promising Photocatalytic Properties

The compound [Co₄(C₆H₁₄N₂)₄(μ₄‐S₂)₂(μ₂‐S₂)₄] ( I ) and the pseudo‐polymorph [Co₄(C₆H₁₄N₂)₄(μ₄‐S₂)₂(μ₂‐S₂)₄] ? 4 H₂O ( II ) were obtained under solvothermal conditions (C₆H₁₄N₂=trans‐1,2‐diaminocyclohexane). The structures feature S₂^2? ions exhibiting two different coordination modes. Terminal S₂^2? entities join two Co³⁺ centres in a μ₂ fashion, whereas the central S₂^2? groups connect four Co³⁺ cations in a μ₄‐ coordination mode. Compound II can be transformed into compound I by heat and storage over P₂O₅ and storing compound I in humid air yields in the formation of compound II . The intermolecular interactions investigated through Hirshfeld surface analysis reveal that besides S???H bonding close contacts are associated with relatively weak H???H interactions. A detailed DFT analysis of the bonding situation explains the long S?S bonds in the μ₄‐bridging S₂^2? units and the short bonds for the S₂^2? moieties in the μ₂‐connecting mode. Photocatalytic hydrogen evolution experiments demonstrate the potential of compound II as catalyst.     

Assessment of the fate of some household micropollutants in urban wastewater treatment plant

Everyday domestic activity is a significant source of water pollution. The presence of six household micropollutants in an urban wastewater treatment plant (WWTP) was assessed in wastewater and sludge. A multi-target analytical method was developed for the quantification of ibuprofen, erythromycin, ofloxacin, 4-nonylphenol, 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan), and sucralose. The micropollutants were extracted from the liquid and solid phases and their concentrations were determined by LC-MS/MS. The efficiency of micropollutants’ removal within a conventional activated sludge process was assessed. From 50 % to 90 % of ibuprofen and erythromycin was removed from the wastewater liquid phase. Their removal can be attributed to biological degradation as they were not found adsorbed on the outlet sludge. Ofloxacin and triclosan were removed from the liquid phase with similar efficiencies; however, they were adsorbed on the sludge, so it was not possible to determine their removal mechanism (whether biodegradation or displacement to solid phase/sequestration). Sucralose was not removed from wastewater (3 μg L^?1 in inlet and outlet liquid phase) and not adsorbed on the sludge. 4-Nonylphenol concentrations were sometimes higher in the WWTP outlet water; this may relate to the degradation of alkylphenol ethoxylates in the wastewater treatment process. 4-Nonylphenol was always present in the outlet sludge.     

Synthesis of the Novel Antidepressant (R)-(-)-Rolipram

Enantioselective synthesis of (R)-Rolipram 1 has been achieved through a conjugate addition of cyanide to enantiomerically pure 2-(2-aryl ethenyl)oxazoline 2, followed by selective reduction of the adduct with NaBH₄-NiCl₂.     

Xestospongienols A–L,Brominated Acetylenic Acids from the Chinese Marine Sponge Xestospongia testudinaria

Chemical examination of the Chinese marine sponge Xestospongia testudinaria resulted in the isolation and characterization of twelve new brominated acetylenic acids, namely xestospongienols A–L ( 1a – 1d, 2a – 2d , and 3a – 3d ), together with the known analog 4 . The structures of xestospongienols A–L were determined on the basis of 1D‐ and 2D‐NMR, IR, and MS analysis in association with the modified Mosher method. The structural patterns are characteristic of brominated unbranched C₁₆‐alkyl chains containing polyene and acetylene moieties.