A Remarkably Simple Class of Imidazolium‐Based Lipids and Their Biological Properties

A series of imidazolium salts bearing two alkyl chains in the backbone of the imidazolium core were synthesized, resembling the structure of lipids. Their antibacterial activity and cytotoxicity were evaluated using Gram‐positive and Gram‐negative bacteria and eukaryotic cell lines including tumor cells. It is shown that the length of alkyl chains in the backbone is vital for the antibiofilm activities of these lipid‐mimicking components. In addition to their biological activity, their surface activity and their membrane interactions are shown by film balance and quartz crystal microbalance (QCM) measurements. The structure–activity relationship indicates that the distinctive chemical structure contributes considerably to the biological activities of this novel class of lipids.     

Improved DNA fragment length estimation in capillary electrophoresis

In CE the charged DNA strands are fractionated according to fragment lengths as they migrate through the capillary, since shorter DNA fragments pass through the sieving matrix faster. Multiplexed internal size standards are used to estimate the size of unknown DNA fragments. In the literature there are statements about migration abnormalities for the 250 and 340 bp fragments in the GeneScan-500 (GS500) internal size standards. Such anomalous migration of size standards could obviously introduce errors in the estimation of unknown fragments. Therefore, a number of analysis programs simply exclude some of these fragments. In the present work we first evaluate the effect of excluding each of the fragments in the internal size standards used in CE. Next, a method which is based on estimating the true values of the anomalous fragments is presented. The results obtained by the new method indicate a significant improvement compared to results obtained when one (or both) of the anomalous fragments in GS500 is (are) excluded or included when estimating the size of unknown DNA fragments. In the higher-molecular-weight region, the average error is reduced from 1.91 bp in ABI GeneMapper (excluding 250 bp) to 0.15 bp in the new method (using the estimated values for 250 and 340 bp). In the lower-molecular-weight region, excluding both fragments will improve the results by an average of 0.74 bp compared to ABI GeneMapper.     

Isomer-specific influences on the composition of reaction intermediates in dimethyl ether/propene and ethanol/propene flame

This work provides experimental evidence on how the molecular compositions of fuel-rich low-pressure premixed flames are influenced as the oxygenates dimethyl ether (DME) or ethanol are incrementally blended into the propene fuel. Ten different flames with a carbon-to-oxygen ratio of 0.5, ranging from 100% propene (phi = 1.5) to 100% oxygenated fuel (phi = 2.0), are analyzed with flame-sampling molecular-beam mass spectrometry employing electron- or photoionization. Absolute mole fraction profiles for flame species with masses ranging from m/z = 2 (H2) to m/z = 80 (C6H8) are analyzed with particular emphasis on the formation of harmful emissions. Fuel-specific destruction pathways, likely to be initiated by hydrogen abstraction, appear to lead to benzene from propene combustion and to formaldehyde and acetaldehyde through DME and ethanol combustion, respectively. While the concentration of acetaldehyde increases 10-fold as propene is substituted by ethanol, it decreases as propene is replaced with DME. In contrast, the formaldehyde concentration rises only slightly with ethanol replacement but increases markedly with addition of DME. Allyl and propargyl radicals, the dominant precursors for benzene formation, are likely to be produced directly from propene decomposition or via allene and propyne. Benzene formation through propargyl radicals formed via unsaturated C2 intermediates in the decomposition of DME and ethanol is negligibly small. As a consequence, DME and ethanol addition lead to similar reductions of the benzene concentration.     

Synthesis and evaluation of dihydroimidazolo and dihydrooxazolo ring-fused 2-pyridones—targeting pilus biogenesis in uropathogenic bacteria

Dihydrothiazolo ring-fused 2-pyridones have previously been shown to inhibit pilus assembly in uropathogenic Escherichia coli. Methods have now been developed to synthesize both dihydroimidazolo and dihydrooxazolo ring-fused 2-pyridones. To obtain the nitrogen analogs, Cbz-protected imidazolines were reacted with an acyl-Meldrum's acid derivative under acidic conditions. To prepare the oxygen analogs, a one-pot procedure was developed that allowed synthesis of dihydrooxazolo ring-fused 2-pyridones starting from acylated serine derivatives. After hydrolysis to their corresponding carboxylic acids and lithium carboxylates, biological evaluation revealed that the sulfur could be replaced by an oxygen atom and still maintains the ability to inhibit pilus assembly in uropathogenic E. coli. However, introducing a secondary amine instead of oxygen resulted in a substantial decrease in biological activity.     

Reactivity of Binary and Ternary Sulfur Halides towards Transition-Metal Compounds

Binary sulfur fluorides exhibit an interesting reactivity towards transition metal complexes. They open up routes for the generation of sulfur-containing building blocks. Often ligands with particular properties can be constructed. This includes their ability to transfer sulfur atoms or polysulfide units as well as fluorination reactions. This Minireview provides an insight into the reactivity of the binary and ternary sulfur halides S₂Cl₂, SCl₂, SF₄, SF₆ and SF₅Cl towards transition-metal compounds.     

Enantioselective Total Synthesis of (−)-Finerenone Using Asymmetric Transfer Hydrogenation

(−)-Finerenone is a nonsteroidal mineralocorticoid receptor antagonist currently in phase III clinical trials for the treatment of chronic kidney disease in type 2 diabetes. It contains an unusual dihydronaphthyridine core. We report a 6-step synthesis of (−)-finerenone, which features an enantioselective partial transfer hydrogenation of a naphthyridine using a chiral phosphoric acid catalyst with a Hantzsch ester. The process is complicated by the fact that the naphthyridine exists as a mixture of two atropisomers that react at different rates and with different selectivities. The intrinsic kinetic resolution was converted into a kinetic dynamic resolution at elevated temperature, which enabled us to obtain (−)-finerenone in both high yield and high enantioselectivity. DFT calculations have revealed the origin of selectivity.