Hemiaminals as substrates for sulfur ylides: direct asymmetric syntheses of functionalised pyrrolidines and piperidines

Phenyl stabilised chiral sulfur ylides react with five-membered-ring hemiaminals to give functionalised pyrrolidines directly with high enantioselectivity. The reaction can be diverted to give piperidines instead by isolation of the intermediate epoxide and treatment with TMSOTf.     

Direct separation of boron from Na- and Ca-rich matrices by sublimation for stable isotope measurement by MC-ICP-MS

An improved technique for precise and accurate determination of boron isotopic composition in Na-rich natural waters (groundwater, seawater) and marine biogenic carbonates was developed. This study used a ‘micro-sublimation’ technique to separate B from natural sample matrices in place of the conventional ion-exchange extraction. By adjusting analyte to appropriate pH, quantitative recovery of boron can be achieved (>98%) and the B procedural blank is limited to <8 pg. An additional mass bias effect in MC-ICP-MS was observed which could not be improved via the standard-sample-standard bracketing or the ‘pseudo internal’ normalization by Li. Therefore a standard other than NBS SRM 951 was used to monitor plasma condition in order to maintain analytical accuracy. An isotope cross-calibration with results from TIMS shows that the space-charge mass bias on MC-ICP-MS can be successfully corrected using off-line mathematical manipulation. Several reference materials, including the seawater IAPSO and two groundwater standards IAEA-B-2 and IAEA-B-3, were used to validate this approach. We found that the δ¹¹B of the reference coral JCp-1 was 24.22 ± 0.28‰, corresponding to seawater pH based on the coral δ¹¹B-pH function.     

Selective hydrophobic pocket binding observed within the carbonic anhydrase II active site accommodate different 4-substituted-ureido-benzenesulfonamides and correlate to inhibitor potency

4-Substituted-ureido benzenesulfonamides showing inhibitory activity against carbonic anhydrase (CA, EC 4.2.1.1) II between 3.3-226 nM were crystallized in complex with the enzyme. Hydrophobic interactions between the scaffold of the inhibitors in different hydrophobic pockets of the enzyme were observed, explaining the diverse inhibitory range of these derivatives.     

Delineation of the factors governing reactivity and selectivity in epoxide formation from ammonium ylides and aldehydes

Diastereoselectivity in reactions of aryl-stabilised ammonium ylides are highly sensitive to the nature of the amine and the ylide substituent. DFT calculations are consistent with a mechanism in which reversibility in betaine formation [despite the high energy (and therefore instability) of ammonium ylides] is finely balanced due to the high barrier to ring closure.     

Reversed-phase liquid chromatography using mandelic acid as an eluent for the determination of uranium in presence of large amounts of thorium

Studies were carried out for the separation of uranium (U) and thorium (Th) on reversed-phase (RP) C₁₈ columns using mandelic acid as an eluent. Retention of thorium–mandelate on the unmodified stationary phase was found to be greater than that of uranyl–mandelate under the pH conditions employed. Th retention capacity of the stationary phase was determined as a function of pH and MeOH content of the mobile phase. The optimised parameters allowing U elution prior to Th were utilized for the determination of small amounts of U in the presence of large amounts of Th. The method has been used for the determination of U in synthetic samples with Th/U amount ratios up to 100,000 (10 μg/g of U) without any pre-separation, employing a particulate C₁₈ column. Effect of concentration of ion interaction reagents (IIRs) on the retention was studied to understand the mechanism of adsorption of their mandelate complexes onto the stationary phase. The experiments conducted unequivocally prove that thorium–mandelate complex is neutral whereas uranyl–mandelate complex is anionic in nature.     

Cluster Head Selection in Heterogeneous Wireless Sensor Network Using a New Evolutionary Algorithm

Wireless Personal Communications - In wireless sensor network (WSN), limited energy resources with the nodes is a complex challenge as far as data routing, collecting and aggregating the data is...     

Hiding clinical information in medical images: an enhanced encrypted reversible data hiding algorithm grounded on hierarchical absolute moment block truncation coding

Multidimensional Systems and Signal Processing - Reversible data hiding in the encrypted domain has attracted a lot of consideration because of the necessity for content security and protection...     

Sustainable feasibility of waste printer ink to magnetically separable iron oxide–doped nanocarbons for styrene oxidation

A simpler cost-effective method for the isolation of magnetically separable ‘self-doped iron oxide nanocarbons’ (FeO-NC) from waste printer ink (used as a carbon source material which is available free of cost) is discussed here. The process involves carbonization of waste printer ink in a muffle furnace at ~600 °C to obtain FeO-NC. The as-prepared FeO-NC has been investigated as an efficient heterogeneous catalyst for the long-known important organic reaction involving transformation of styrene to benzaldehyde in a quantitative yield (~70%). Importantly, FeO-NC were magnetically separable along with good recyclability, which supports the sustainability of reported process.     

Synthesis and structural studies of some first row transition metal complexes of acetone nicotinoyl hydrazone

Summary Acetone nicotinoyl hydrazone (ANII) complexes of the types M(ANH)Cl₂ · nEtOH and M(ANH-H)₂ H₂O (where M = Mn^II Fe^II, Co^II, Ni^II, Cu^II or Zn^II and n = 0,1 or 2) have been prepared and their structures studied by molar conductance, i.r. and electronic spectra, and room temperature magnetic measurements. All the complexes arc nonionic in a 0.001 M solution of formic acid. Magnetic and electronic spectral studies show that all the complexes are spin-free regular or distorted octahedra except Mn(ANH)Cl₂ and Co(ANH)CI₂ which are tetrahedral. The distorted octahedral geometry of Cu(ANH-H)₂ · H2O has also been confirmed from its sold state e.s.r spectrum at 77 K. From i.r. spectral studies, ANH has been found to act as a tridentate ligand in all the complexes except Mn(ANH)Cl₂ where it behaves as a bidentate ligand.     

Finite fringe moiré deflectometry for the measurement of radius of curvature: an alternative approach

Moiré deflectometry, based on infinite fringe detection, is a sensitive and advantageous method for the precise measurement of optical parameters. An alternative approach, based on accurate finite-fringe detection moiré deflectometry, is described for the measurement of radius of curvature. An error estimation of the method, supported by experimental verification, is also presented. Extension of the method for the measurement of a long radius of curvature has also been suggested.