Helvetica Chimica Acta最新文献

Amoxicillin is a frequently used beta-lactam antibiotic and at the same time a fragile analyte. Aim of this work was to investigate the sensitive properties of amoxicillin in biological samples and validate a quantification method for amoxicillin in soft tissue samples. Simple protein precipitation and 2D-High performance liquid chromatography coupled to tandem mass spectrometry was used for sample preparation and analysis. The formation of a covalent amoxicillin methanol-adduct could be observed in varying extents depending on matrix and sample preparation method. In-Source Products (ISPs) were investigated in plasma, soft tissue, and water and no differences could be observed. We successfully validated a method for amoxicillin determination in tissue samples using the sum of 2 ISPs of amoxicillin for quantification. 37 study samples of different deep-seated infections could be analyzed. Measured amoxicillin concentrations ranged from below 0.5 mg/kg up to 87 mg/kg. Concentrations in abscesses were lower than in other infections.

Controlling the charge state of biomolecules in high vacuum enables experiments in molecular physics and physical chemistry, particularly in applications of mass spectrometry, trapping and cooling, spectroscopy and matter-wave interferometry. Here we investigate the synthesis, verification and gas phase photolysis of nitrodibenzofuranmethyl aryl ether derivatives. These photocages are chosen because their absorption maximum can be tuned to near 355 nm, where intense pulsed laser light is available. We demonstrate efficient gas-phase cleavage of a photoactive nitrodibenzofuranmethyl aryl ether derivative, both free and attached to oxytocin. This enables the neutralization of a polypeptide derivative in high vacuum using a wavelength outside the absorption spectrum of natural amino acids.

Functional molecular electronics require molecular design that provides integrity and stability. In this work, we explored two types of single molecule devices differing in anchoring to the conducting leads. Single molecule conductance was measured by STM break junction method and the molecular conductor was composed of the redox active anthraquinone center (switching element) containing either 4-pyridyl or p-phenylene thioacetate anchoring groups. The experimental results were supported by quantum chemical charge transport calculations. Molecular junctions containing 4-pyridyl anchors displayed two stable configurations with conductance values of 4.9 nS and 20 pS, respectively. Molecules anchored via p-phenylene thioacetate groups led to one main junction configuration with conductance of 0.1 nS. Junctions employing 4-pyridyl anchoring groups had higher junction formation probability, which in combination with lower conductance makes them better candidates for switching purposes.

Oligoprolines adopt the well-defined polyproline II (PPII) helical conformation, even at a short chain length of six residues. These rigid peptides are versatile molecular rulers and scaffolds, yet there has been great difficulty in obtaining single crystals for X-ray crystal structure analysis to probe their conformation in the solid state. Here, we report a crystal structure of an oligoproline hexamer bearing an N-terminal terephthalic acid moiety. Comparison with that of a previously obtained crystal structure of a closely related hexaproline revealed influence of the terminal functional groups and the solvent on the crystal packing.

The development of a safe, efficient and scalable continuous-flow-chemistry protocol for the O-difluoromethylation of two 3-hydroxypyridine building blocks is described. This example highlights that continuous flow chemistry has become firmly established within Novartis Biomedical Research, and when implemented appropriately can enable the continuous supply of material from the first realization of a potentially interesting intermediate within a discovery project all the way through to clinical evaluation.

We report herein an unprecedented and scalable synthetic method for the production of specific aminoquinoline compounds with potential applications as sweetness-enhancing agents. The first strategy involves the reaction of ortho-aminobenzonitriles with β-ketoesters in the presence of stoichiometric amounts of FeCl₃. Alternatively, the second strategy focuses on an enamine synthesis using alkyl acetoacetate and aminobenzonitrile. The resulting enaminonitrile is then converted into aminoquinoline under basic conditions. This newly developed process yields the desired compounds with an overall yield above 45 % over five steps with high purity.

The emergence of photoredox chemistry has enabled the development of previously inaccessible synthetic transformations. Despite the popularity of photoredox chemistry, commercial photoreactors remain expensive. As a result, most academic research groups resort to self-built, not easily replicable reactor designs, jeopardizing the reproducibility and accessibility of photochemical research. To address these issues, this work introduces an easily replicable and modular open-source photoreactor optimized for lab-scale photochemical synthesis. The reactor is operationally simple, operates consistently and reproducibly, and is inexpensive to manufacture. Our design integrates active temperature regulation, an exchangeable vial rack, and customizable light sources into a hybrid structure of machined aluminum, 3D-printed parts, and commercially available components. The open-source reactor with detailed 3D CAD files on GitHub is designed to make research in the field of photochemistry more accessible and reproducible.