A stereoselective, Sm(II)-mediated approach to decorated cis-hydrindanes: synthetic studies on faurinone and pleuromutilin

The cis-hydrindane motif is found in a number of natural products that display important biological activity. A flexible, stereoselective approach to the framework has been developed that features highly diastereoselective, SmI(2)-mediated cyclisations. The strategy has been exploited in the first synthesis of the proposed structure of faurinone and an approach to the skeleton of the antibacterial natural product, pleuromutilin.     

Classical and quantum properties of a two-sphere singularity

Recently Böhmer and Lobo have shown that a metric due to Florides, which has been used as an interior Schwarzschild solution, can be extended to reveal a classical singularity that has the form of a two-sphere. Here the singularity is shown to be a naked scalar curvature singularity that is both timelike and gravitationally weak. It is also shown to be a quantum singularity because the Klein–Gordon operator associated with quantum mechanical particles approaching the singularity is not essentially self-adjoint.     

A Polymer‐Based Electrochemical DNA Biosensor for Salmonella: Preparation,Characterization and Calibration

In this paper, we present the results of the use of bifunctional polymeric films of polystyrene (10.3 KD–49.5 KD) to anchor oligo sequences of various lengths (15, 35 and 70‐mer). The polymers were prepared by radical polymerization with 4,4′‐azobis(4‐cyanovaleric acid) as initiator and 3‐Carboxy PROXYL to control the molecular weight and polydispersity. They were further modified with N‐hydroxysuccinimide to anchor the (5′‐AmMC₁₂) oligos. The anchoring reaction was done on a polymer‐modified glassy carbon electrode. The probes were hybridized with their ferrocene‐labeled complementary sequences. The hybridization reaction was followed by Osteryoung square wave voltammetry (OSWV). The calibration curve showed a narrow and sharp linear range between (5.7–8.0)×10^?7 M and a detection limit around 0.55 µM.     

Syntheses and properties of complexes with bis(2,2′-bipyridyl)ruthenium(II) moieties coordinated to 4,4′:2′,2′′:4′′,4′′′-quaterpyridinium ligands

Eleven new complexes of the form cis-[Ru^II(bpy)₂(L^A)]⁴⁺ (bpy = 2,2′-bipyridyl; L^A = a pyridinium-substituted bpy derivative) have been prepared and isolated as their PF₆⁻ salts. Characterisation involved various techniques including ¹H NMR spectroscopy and MALDI mass spectrometry. The UV-Vis spectra show intense intraligand π → π^∗ absorptions and metal-to-ligand charge-transfer (MLCT) bands with two distinct maxima in the visible region. Small shifts in the MLCT bands correlate with the electron-withdrawing strength of the ligand L^A. Cyclic voltammograms show quasi-reversible or reversible Ru^III/II oxidation waves, and two or more ligand-based reductions with varying degrees of reversibility. The variations in the redox potentials correlate with changes in the structure of L^A, and also with the MLCT energies. Differential pulse voltammetry allows the first reduction process for two of the complex salts to be resolved into two peaks. Single-crystal X-ray structures have been solved for three of the new complex salts and also for a pro-ligand salt. Two carboxylate-functionalised compounds have been tested as photosensitizers on TiO₂-coated electrodes, but show only negligible efficiencies, in accord with expectations.     

Phosphonate ligands encourage a platonic relationship between cobalt(II) and alkali metal ions

Two new cobalt(ii) cages are reported where the metal core has a high symmetry related to a Platonic solid; the choice of alkali metal used in the base used for deprotonation appears to influence the resulting structures.