Copper(II) Triflate Catalyzed Amination of 1,3‐Dicarbonyl Compounds

A method to prepare α,α‐acyl amino acid derivatives efficiently by Cu(OTf)₂+1,10‐phenanthroline (1,10‐phen)‐catalyzed amination of 1,3‐dicarbonyl compounds with PhI?NSO₂Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper–nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α‐aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3‐styryl‐2‐benzoyl‐L ‐alanine.     

Micro-patterned porous substrates for cell-based assays

In the search for new therapeutic chemicals, lab-on-a-chip systems have recently emerged as innovative and efficient tools for cell-based assays and high throughput screening. Here, we describe a novel, versatile and simple device for cell-based assays at the bench-top. We created spatial variations of porosity on the surface of a membrane filter by microcontact printing with a biocompatible polymer (PDMS). We called such systems Micro-Printed Membranes (μPM). Active compounds dispensed on the porous areas, where the membrane pores are not clogged by the polymer, can cross the membrane and reach cells growing on the opposite side. Only cells immediately below those porous areas could be stimulated by chemicals. We performed proof-of-principle experiments using Hoechst nuclear staining, calcein-AM cell viability assay and destabilization of the cytoskeleton organisation by cytochalasin B. Resulting fluorescent staining properly matched the drops positioning and no cross-contaminations were observed between adjacent tests. This well-less cell-based screening system is highly flexible by design and it enables multiple compounds to be tested on the same cell tissue. Only low sample volumes in the microlitre range are required. Moreover, chemicals can be delivered sequentially and removed at any time while cells can be monitored in real time. This allows the design of complex, sequential and combinatorial drug assays. μPMs appear as ideal systems for cell-based assays. We anticipate that this lab-on-chip device will be adapted for both manual and automated high content screening experiments.     

Deformation of proper actions on reductive homogeneous spaces

Let G be a real reductive Lie group and H a closed reductive subgroup of G. We investigate the deformation of standard compact quotients of G/H, that is, of quotients of G/H by discrete groups Γ that are uniform lattices in some closed reductive subgroup L of G acting properly and cocompactly on G/H. For L of real rank 1, we prove that after a small deformation in G, such a group Γ keeps acting properly discontinuously and cocompactly on G/H. More generally, we prove that the properness of the action of any convex cocompact subgroup of L on G/H is preserved under small deformations, and we extend this result to reductive homogeneous spaces G/H over any local field. As an application, we obtain compact quotients of SO(2n, 2)/U(n, 1) by Zariski-dense discrete subgroups of SO(2n, 2) acting properly discontinuously.     

Signal enhancement in laser diode thermal desorption‐triple quadrupole mass spectrometry analysis using microwell surface coatings

Laser‐diode thermal desorption (LDTD) is an ionization source usually coupled to triple quadrupole mass spectrometry (QqQMS) and specifically designed for laboratories requiring high‐throughput analysis. It has been observed that surface coatings on LDTD microwell plates can improve the sensitivity of the analysis of small polar molecules. The objective of the present study is to understand and quantify the effect of microwell surface coatings on signal intensity of small organic molecules of clinical, environmental, and forensic interest. Experiments showed that the peak areas of diclofenac, chloramphenicol, salicylic acid, and 11‐nor‐9‐carboxy‐Δ⁹‐tetrahydrocannabinol obtained by LDTD‐QqQMS increased by up to 3 orders of magnitude when using microwells coated with ethylenediaminetetraacetic acid (EDTA). Tests with different chelating agents and polytetrafluoroethylene as microwell surface coatings showed that nitrilotriacetic acid gave significantly higher peak areas for five out of the nine compounds that showed signal enhancement using chelating agents as coatings. Scanning electron microscopy studies of EDTA‐coated and uncoated microwells showed that analytes deposited in the former formed more uniform and thinner films than in the latter. The enhancement effect of surface coatings in LDTD‐QqQMS was explained mainly by the formation of homogenous and thinner layers of nanocrystals of analytes that are easier to desorb thermally than the layers formed when the analytes dry in direct contact with the bare stainless‐steel surface. Chemisorption of some analytes to the stainless‐steel surface of the microwell plate appeared to be a minor factor. Surface coatings widen the number of compounds analyzable by LDTD‐QqQMS and can also improve sensitivity and limits of detection.     

Rapid synthesis of new 2-methyl-7-nitro-5-substituted-2,3-dihydroimidazo[5,1-b]oxazole as potential antibacterial drugs through one-pot cyclization and Suzuki–Miyaura coupling

Original 2-methyl-7-nitro-5-substituted-2,3-dihydroimidazo[5,1-b]oxazoles were prepared by reacting 1-(2,5-dibromo-4-nitro-1H-imidazol-1-yl)propan-2-ol and various arylboronic acids through “one-pot” cyclization and Suzuki–Miyaura reactions under microwave irradiation.     

Determination of explosives in environmental water samples by solid-phase microextraction-liquid chromatography

When explosives are present in natural aqueous media, their concentration is usually limited to trace levels. A preconcentration step able to remove matrix interferences and to enhance sensitivity is therefore necessary. In the present study, we evaluated solid-phase microextraction (SPME) technique for the recovery of nine explosives from aqueous samples using high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Several parameters, including adsorption and desorption time, coating type, rate of stirring, salt addition, and pH, were optimized to obtain reproducible data with good accuracy. Carbowax coating was the only adsorbent found capable of adsorbing all explosives including nitramines. Method detection limits (MDL) were found to range from 1 to 10 microg/L, depending on the analyte. SPME/HPLC-UV coupling was then applied to the analysis of natural ocean and groundwater samples and compared to conventional solid-phase extraction (SPE/HPLC-UV). Excellent agreement was observed between both techniques, but with an analysis time around five times shorter, SPME/HPLC-UV was considered to be applicable for quantitative analysis of explosives.     

Lanthanide mono(borohydride) complexes of diamide-diamine donor ligands: novel single site catalysts for the polymerisation of methyl methacrylate

Samarium chloride and borohydride complexes of the diamide-diamine ligands (2-C5H4N)CH2N(CH2CH2NR)2(R = SiMe3 or mesityl) are described; the borohydride compounds are the first polydentate amide-supported single component lanthanide catalysts for the controlled polymerisation of polar monomers, and also represent the first lanthanide borohydride complex for the polymerisation of methyl methacrylate.