Photoswitching the Cytotoxic Properties of Platinum(II) Compounds

The photoactivation of potential anticancer metal complexes is a hot topic of current research as it may lead to the development of more selective drugs. Photoactivated chemotherapy (PACT) with coordination compounds is usually based on a (photo)chemical reaction taking place at the metal center. Herein, a new strategy is exploited that consists of “photomodifying” a ligand coordinated to metal ions. Platinum(II) complexes from photoswitchable 1,2‐dithienylethene‐containing ligands have been prepared, which exhibit two interconvertible photoisomeric forms that present distinct DNA‐interacting properties and cytotoxic behaviors.     

Separation and characterization of oxidized isomeric lipid–peptide adducts by ion mobility mass spectrometry

Phospholipids are major components of cell membranes and lipoprotein complexes. They are prone to oxidation by endogenous and exogenous reactive oxygen species yielding a large variety of modified lipids including small aliphatic and phospholipid bound aldehydes and ketones. These carbonyls are strong electrophiles that can modify proteins and, thereby, alter their structures and functions triggering various pathophysiological conditions. The analysis of lipid–protein adducts by liquid chromatography‐MS is challenged by their mixed chemical nature (polar peptide and hydrophobic lipid), low abundance in biological samples, and formation of multiple isomers. Thus, we investigated traveling wave ion mobility mass spectrometry (TWIMS) to analyze lipid–peptide adducts generated by incubating model peptides corresponding to the amphipathic β₁ sheet sequence of apolipoprotein B‐100 with 1‐palmitoyl‐2‐(oxo‐nonanoyl)‐sn‐glycerophosphatidylcholine (PONPC). The complex mixture of peptides, lipids, and peptide–lipid adducts was separated by TWIMS, which was especially important for the identification of two mono‐PONPC‐peptide isomers containing Schiff bases at different lysine residues. Moreover, TWIMS separated structural conformers of one peptide–lipid adduct possessing most likely different orientations of the hydrophobic sn‐1 fatty acyl residue and head group of PONPC, relative to the peptide backbone. Copyright © 2015 John Wiley & Sons, Ltd.     

1,3‐Benzothiazoles as Antimicrobial Agents

Starting from 2‐amino‐1,3‐mercaptobenzothiazoles recently reported ( 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h ), a series of the corresponding 2‐mercapto‐1,3‐benzothiazole isosters ( 2a , 2b , 2c , 2d , 2e , 2f , 2g , 2h ) were screened for their in vitro antibacterial and antifungal activities. Results underline that the presence of the mercapto moiety at the 2‐position of the heterocyclic nucleus is crucial for activity against bacteria. The biological screening against Candida spp. identified commercial 2f as the most promising compound as antifungal against Candida albicans and tropicalis. Molecular modeling studies supported these results. Then, to enlarge structure‐activity relationship (SAR) studies on series 1 , newly synthesized compounds ( 1k , 1l , 1m , 1n , 1o , 1p ) were reported. All the compounds belonging to this series and bearing a bulky substituent at the 6‐position of the aryl moiety showed high antifungal activity.     

Conservation laws of two coupled non-linear oscillators

This paper presents a novel approach to obtaining a complete set of time-dependent expressions for approximate conservation laws of two weakly non-linear coupled oscillators. The procedure developed for a non-resonant case is based on the field method concept of deriving a conservation law from an incomplete solution of a partial differential equation. Due to the non-linearity of the system being considered, this concept is combined with the multiple variable expansion procedure.     

Single‐Crystal‐to‐Single‐Crystal Transition in an Enantiopure [7]Helquat Salt: The First Observation of a Reversible Phase Transition in a Helicene‐Like Compound

Here it is reported that crystals of an enantiopure [7]helquat salt undergo reversible thermal solid–solid phase transition at 404 K. Differential scanning calorimetry (DSC), capillary electrophoresis (CE), and X‐ray diffraction analysis were used to unravel the mechanistic details of this process. The single‐crystal‐to‐single‐crystal course enabled direct monitoring of the structural changes by in situ variable‐temperature X‐ray diffraction, thus providing the first direct evidence of a solid phase transition in a helicene‐like compound.     

Synthesis and Catalytic Use of Gold(I) Complexes Containing a Hemilabile Phosphanylferrocene Nitrile Donor

Removal of the chloride ligand from [AuCl( 1 ‐κP)] ( 2 ) containing a P‐monodentate 1′‐(diphenylphosphanyl)‐1‐cyanoferrocene ligand ( 1 ), by using silver(I) salts affords cationic complexes of the type [Au( 1 )]X, which exist either as cyclic dimers [Au( 1 )]₂X₂ ( 3 a , X=SbF₆; 3 c , X=NTf₂) or linear coordination polymers [Au( 1 )]_nX_n ( 3 a′ , X=SbF₆; 3 b′ , X=ClO₄), depending on anion X and the isolation procedure. As demonstrated for 3 a′ , the polymers can be readily cleaved by the addition of donors, such as Cl^?, tetrahydrothiophene (tht) or 1 , giving rise to the parent compound 2 , [Au(tht)( 1 ‐κP)][SbF₆] ( 5 a ) or [Au( 1 ‐κP)₂][SbF₆] ( 4 a ), respectively, of which the last two compounds can also be prepared by stepwise replacement of tht in [Au( 1 ‐κP)₂][SbF₆]. The particular combination of a firmly coordinated (phosphane) and a dissociable (nitrile) donor moieties renders complexes 3/3′ attractive for catalysis because they can serve as shelf‐stable precursors of coordinatively unsaturated Au^I fragments, analogous to those that result from the widely used [Au(PR₃)(RCN)]X catalysts. The catalytic properties of the Au‐ 1 complexes were evaluated in model annulation reactions, such as the synthesis of 2,3‐dimethylfuran from (Z)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol and oxidative cyclisation of alkynes with nitriles to produce 2,5‐disubstituted 1,3‐oxazoles. Of the compounds tested ( 2 , 3 a′ , 3 b′ , 3 a , 4 a and 5 a ), the best results were consistently achieved with dimer 3 c , which has good solubility in organic solvents and only one firmly bound donor at the gold atom. This compound was advantageously used in the key steps of annuloline and rosefuran syntheses.     

Automated in-syringe single-drop head-space micro-extraction applied to the determination of ethanol in wine samples

A novel approach of head-space single-drop micro-extraction applied to the determination of ethanol in wine is presented. For the first time, the syringe of an automated syringe pump was used as an extraction chamber of adaptable size for a volatile analyte. This approach enabled to apply negative pressure during the enrichment step, which favored the evaporation of the analyte. Placing a slowly spinning magnetic stirring bar inside the syringe, effective syringe cleaning as well as mixing of the sample with buffer solution to suppress the interference of acetic acid was achieved.     

Cycloaddition Reactions of Deoxyribosylpropynoates

Pure anomers of either α or β 3-(2-deoxyribofuranosyl)propynoates reacted with the tetramethylcyclobutadiene–aluminum trichloride complex to yield the corresponding diastereoisomeric Dewar benzenes. Thermal- or ultraviolet light–initiated rearrangement gave rise to highly substituted C-aryldeoxyribosides as single anomers. The same compounds as well as other substituted deoxyribosides were obtained also by transition metal–mediated cycloaddition reactions.