Monatshefte Fur Chemie最新文献

Targeted cancer treatment is a promising, less invasive alternative to chemotherapy as it is precisely directed against tumor cells whilst leaving healthy tissue unaffected. The plant-derived enzyme horseradish peroxidase (HRP) can be used for enzyme prodrug cancer therapy with indole-3-acetic acid or the analgesic paracetamol (acetaminophen). Oxidation of paracetamol by HRP in the presence of hydrogen peroxide leads to N-acetyl-p-benzoquinone imine and polymer formation via a radical reaction mechanism. N-acetyl-p-benzoquinone imine binds to DNA and proteins, resulting in severe cytotoxicity. However, plant HRP is not suitable for this application since the foreign glycosylation pattern is recognized by the human immune system, causing rapid clearance from the body. Furthermore, plant-derived HRP is a mixture of isoenzymes with a heterogeneous composition. Here, we investigated the reaction of paracetamol with defined recombinant HRP variants produced in E. coli, as well as plant HRP, and found that they are equally effective in paracetamol oxidation at a concentration ≥ 400 µM. At low paracetamol concentrations, however, recombinant HRP seems to be more efficient in paracetamol oxidation. Yet upon treatment of HCT-116 colon carcinoma and FaDu squamous carcinoma cells with HRP-paracetamol no cytotoxic effect was observed, neither in the presence nor absence of hydrogen peroxide.

Supplementary information: The online version contains supplementary material available at 10.1007/s00706-021-02848-x.

A new method for determination of selected heavy metals (Cd, Pb, Cu, Zn, and Ni) in honey bee venom was developed. Heavy metals are metabolized and incorporated into bee products, including honey and honey bee venom (apitoxin). Their composition reflects contamination of "bee environment", providing information about heavy metal contamination in the neighborhood of human dwellings. Moreover, assessment of bee products contamination is relevant for medicine, as they are a tool for promising therapeutic and chemoprophylactic strategies against COVID-19 (SARS-CoV-2). Owing to the complicated matrix, the developed method consists of wet mineralization with sulfuric acid, nitric acid, under increased temperature, and pressure and subsequent repeated boiling with concentrated nitric acid. Determination of the selected metals was carried out by anodic or cathodic stripping voltammetry on two types of electrodes: pen-type hanging mercury drop electrode (HMDE) and PLA filament with carbon conductive admixture (PLA-C) for 3D printer. Contents of lead and cadmium in all analyzed bee venom samples were on the level of mg kg^-1, of nickel and copper about ten times higher, and of zinc on the level of g kg^-1. The results achieved using HMDE were recorded with average relative standard deviation (RSD) 5.4% (from 3.2% to 8.6%) and using PLA-C 11.8% (from 6.5% to 18.0%). The results achieved using both electrodes proved to be equivalent with statistical probability higher than 95%.

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In this work, we show that intramolecular hydrogen bonding can be used to stabilize tri-coordinated phosphane-gold(I) complexes. Two molecular structures of 2-(diphenylphosphino)benzoic acid (L) coordinated to a gold(I) atom were determined by single-crystal X-ray diffraction. The linear L-Au-Br shows a standard linear coordination and dimerizes via hydrogen bonds of the carboxylic acid. Upon addition of two additional phosphane ligands the complex [L₃Au]X is formed which is stabilized by three intramolecular -C(O)O-H ^… X hydrogen bonds as proven by the X-ray structure of the respective chlorido-complex. X-ray powder diffractograms suggest the same structure also for X^- = Br^- and I^-.

Supplementary information: The online version contains supplementary material available at 10.1007/s00706-021-02843-2.

Abstract: Decades of chemophobia are taking a high toll on chemistry. As current surveys suggest, people are displaying an irrational desire to live in a world without chemistry, but at the same time are unable to answer trivial chemistry questions. Constant questioning of the importance of chemistry induced by chemophobia leads to a weakening of the identity of chemists and can have negative consequences on the reproduction of chemistry. The need for the support of a positive perception of the chemical profession and an offer of positive examples for self-identification is the result. Everyday communication thus becomes the background on which the determination of the identity of the chemist takes place. The new communication strategy, which we call "heroes of chemistry", aims not only to add a much-needed human touch to chemistry communications, but also to create the conditions for strengthening the identity of the chemist.

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Abstract: The multistep synthesis of a prenylneoflavone through a sequence of the Mitsunobu reaction/Claisen rearrangement/olefin cross-metathesis reaction has been accomplished in 5% yield over six steps starting from commercially available 3-methoxyacetophenone. The sequence is shown to be compatible with a Pechmann condensation which proved to be a robust and cost-effective method for the assembling of the α-pyrone core. The results open doors to a general approach to the prenylneoflavone system starting from phenol and acetophenone derivatives.

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Abstract: A continuous flow procedure for the synthesis of methyl glycosides (Fischer glycosylation) of various monosaccharides using a heterogenous catalyst has been developed. In-depth analysis of the isomeric composition was undertaken and high consistency with corresponding results observed under microwave heating was obtained. Even in cases where addition of water was needed to achieve homogeneity-a prerequisite for the flow experiments-no detrimental effect on the conversion was found. The scalability was demonstrated on a model case (mannose) and as part of the target-oriented synthesis of d-glycero-d-manno heptose, both performed on multigram scale.

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Abstract: The new chiral PNP pincer ligand N ²,N ⁶-bis((3aR, 8aR)-2,2-dimethyl-4,4,8,8-tetraphenyltetrahydro[1,3]dioxolo[4,5-e][1,3,2]dioxaphosphepin-6-yl)pyridine-2,6-diamine (PNP-TADDOL) was synthesized in 80% isolated yield. Complexes of the type [M(PNP-TADDOL)(CO)₃] (M = Cr, Mo, and W) were prepared via a solvothermal approach. This methodology constitutes a fast, simple, and practical synthetic method to obtain complexes of that type in high isolated yields. The X-ray structure of the molybdenum complex is presented.

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Abstract: Stable radicals in organic conjugated molecules are of great interest due to their magnetic signals and broad optical absorptions. In this paper, we report on naphthalene, benzoperylene, perylene, terrylene, and quaterrylene carboximides, reduced under controlled conditions, where stable metal-free solid salts of radical anions could be obtained forming darkly colored solutions with line-rich UV/Vis/NIR spectra and exhibiting special magnetic properties. The most bathochromic shift of the absorption maxima extend from 760 until 1700 nm. Persistent paramagnetic properties of the solids were observed and temperature-dependent susceptibilities are measured.

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Abstract: A series of neutral bis- and cationic tris-carbonyl complexes of the types cis-[M(κ³ P,N,P-PNP)(CO)₂Y] and [M(κ³ P,N,P-PNP)(CO)₃]⁺ was prepared by reacting [M(CO)₅Y] (M = Mn, Re; Y = Cl or Br) with PNP pincer ligands derived from the 2,6-diaminopyridine, 2,6-dihydroxypyridine, and 2,6-lutidine scaffolds. With the most bulky ligand PNP^NH-tBu, the cationic square-pyramidal 16e bis-carbonyl complex [Mn(PNP^NH-tBu)(CO)₂]⁺ was obtained. In contrast, in the case of rhenium, the 18e complex [Re(PNP^NH-tBu)(CO)₃]⁺ was formed. The dissociation of CO was studied by means of DFT calculation revealing in agreement with experimental findings that CO release from [M(κ³ P,N,P-PNP)(CO)₃]⁺ is in general endergonic, while for [Mn(κ³ P,N,P-PNP^NH-tBu)(CO)₃]⁺, this process is thermodynamically favored. X-ray structures of representative complexes are provided.

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