Halogenated secondary metabolites from Laurencia obtusa

A new sesquiterpene (1), and a halogenated C15 acetogenin (2), a stereoisomer of neoisoprelaurefucin were isolated from Laurencia obtusa. Four known compounds laurencienyne (3), rogiolenyne B (4), obtusenol (5), and (3E)-dactomelyne (6) were also isolated from this alga. Rogiolenyne B (4) and (3E)-dactomelyne (6) were found for the first from this species. The structures of these compounds were elucidated by spectroscopic methods. The unambiguous assignments of the 1H and 13C NMR spectral data of (5) and 13C NMR data of (6) were also reported for the first time.     

Preparation and characterization of PEPPSI-palladium N-heterocyclic carbene complexes using benzimidazolium salts catalyzed Suzuki–Miyaura cross coupling reaction and their antitumor and antimicrobial activities

New palladium complexes were efficiently synthesized from the reaction of benzimidazolium salts 2a–e, potassium carbonate (K₂CO₃) and palladium chloride (PdCl₂) in pyridine (for 3a–e). The catalytic activity of these complexes in a catalytic system including palladium complexes and K₂CO₃ in DMF-H₂O was evaluated in Suzuki–Miyaura cross-coupling reactions of aryl bromides and chlorides with phenylboronic acid. Our novel complexes show excellent catalytic activities with high turnover numbers (TON) and high turnover frequencies (TOF) (e.g. for the Suzuki–Miyaura reaction: TON up to 370 and TOF up to 123.3?h^?1). Both benzimidazolium salts 2a–e and complexes 3 have been characterized using spectroscopic data and elemental analysis. The antimicrobial activity of the N-heterocyclic carbene palladium complexes 3a–e varies with the nature of the ligands. Also, the IC₅₀ values of both, complexes (3a–e) and benzimidazoles 2a–e, have been determined. In addition, the new palladium complexes were screened for their antitumor activity. Complexes 3e and 3d exhibited the highest antitumor effect with IC₅₀ values 6.85?μg/mL against MCF-7 and 10.75?μg/mL against T47D, respectively.     

Evaluation of Multicenter Nuclear Attraction Integrals by the Use of Translation Formula for Slater Type Orbitals

By the use of translation formula for Slater type orbitals (STOs), three-center nuclear attraction integralsare represented in terms of two-center overlap and nuclear attraction integrals. The computing results for the formulapresented here has been tested under wide changes in molecular parameters and good convergence has been obtainedwith the prior literature.     

Laurenyne,a new acetylene from Laurencia obtusa: crystal structure and absolute configuration

Laurenyne, a new chloroacetylene from the red form of the alga Laurencia obtusa has been identified and its crystal structure determined.     

Efficient synthesis of new perfluorinated or hybrid amphiphilic surfactants

A very simple pathway for the preparation of amphiphilic analogues of natural bioactive peptidoamines such as carnosine (β-alanylhistidine) or carcinine (β-alanylhistamine), is presented. The strategy makes it possible to synthesise original bialkylchain or trialkylchain perfluorinated surfactants with or without perhydrogenated chains.     

Symbolic Calculation of Two‐Center Overlap Integrals Over Slater‐Type Orbitals

Two‐center overlap integrals over Slater type orbitals (STOs) have been expressed in terms of the well‐known Mulliken's integrals B_n(pt) using Rodrigues's formula for normalized associated Legendre functions. A computer program is written in Mathematica 4.0 for the evaluation of two‐center overlap integrals over STOs. Using this computer program, symbolic tables are presented for two‐center overlap integrals up to quantum numbers 1 ≤ n,n′ ≤ 3, 0 ≤ l,l′ ≤ 2, ?2 ≤ m,m′ ≤ 2. Numerical results of this work, for some quantum sets, have also been compared with prior literature and best agreement achieved with recent works of Barnett while some discrepancies were obtained with works of Öztekin et al. and Guseinov et al.     

A Novel Approach for the Temperature Dependence of the Saturated Signal Power in EDFAs

The temperature dependence of the saturated signal power for the ⁴I_13/2 → ⁴I_15/2 transition in erbium-doped fiber amplifiers (EDFAs) pumped at 980 nm and 1480 nm pumping wavelengths within a temperature range from −20 to 60°C are investigated by a novel approach. This approach is based on the temperature dependence of the saturated signal power. The influence of pump excited-state absorption (ESA) is inserted into the rate equations so as to investigate a generally situation. For 1480 nm pumping regime, it is seen that the saturated signal power increases more quickly than that of 980 nm pumping regime, with the increasing temperature. The variation in the saturated signal power with temperature is nearly constant at 980 nm pumping regime. In addition, the population inversion with respect to the increasing normalized signal power is examined and it is seen that it is independent temperature for 980 nm but it strongly depends on temperature for 1480 nm especially at lower normalized signal powers.     

Leaching kinetics of electric arc furnace dust in nitric acid solutions

Electric arc furnace dust contains mainly ZnO, ZnFe₂O₄, and iron oxides. In this study, chemical composition of ZnO, ZnFe₂O₄, and Fe₂O₃ and leaching kinetics of ZnO, ZnFe₂O₄, and Fe₂O₃ in HNO₃ solutions were investigated. It was seen that the dissolution of ZnO is very fast, therefore the leaching kinetics of ZnO cannot be determined. Kinetic parameters and model equations were derived for the leaching of ZnFe₂O₄ and Fe₂O_3. Leaching kinetics of ZnFe₂O₄ was explained by the pseudohomogeneous reaction model. Activation energy and order of HNO₃ concentration were found to be as 37.5 kJ mol⁻¹ and 0.37, respectively. The model equation was derived as . It was determined that experimental data for the leaching kinetics of Fe₂O₃ best fit with the shrinking core model (SCM). Activation energy and order of HNO₃ concentration were found to be as 51.5 kJ mol⁻¹ and 0.67, respectively The model equation was derived using SCM as _.     

Novel quasi‐scorpionate ligand structures based on a bis‐N‐heterocyclic carbene chelate core: synthesis,complexation and catalysis

A series of novel quasi‐scorpionate CNC donor ligands, MeC(2‐C₅H₄N){CH₂(imidazole‐R)} (R = methyl, n‐butyl, n‐propenyl), in which a chelating bis(NHC) core is supplemented by a hemi‐labile pyridyl donor, were prepared. The coordination chemistry of these ligands was investigated with silver, palladium, rhodium and iridium. The single crystal X‐ray structures of [Rh(NC₂^Me)(COD)]Cl 8a and [Ir(NC₂^Pr)(COD)]Br 9b were determined. The catalytic potential of the rhodium and iridium complexes was assessed in the transfer hydrogenation of ketones; the iridium complexes, which show superior performance, form very effective and stable catalysts. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and Structural Characterization of Singly,Doubly, and Triply Bridged Derivatives of Hexachlorocyclotriphosphazene with Bis(2-hydroxyethyl) Ether and 2,2-dimethylpropane-1,3-diol

Abstract

The reactions of hexachlorocyclotriphosphazene, N₃P₃Cl₆ (1), with 2,2-dimethylpropane-1,3-diol (2), and bis(2-hydroxyethyl) ether (3) have been previously reported. Although both reactions gave the expected spiro, ansa, and bridged type products, open-chain and triply bridged derivatives from both systems and singly bridged derivatives from 2,2-dimethylpropane-1,3-diol (2) were not isolated, and doubly bridged compounds were only detected in trace amounts in both systems. However, in a subsequent reinvestigation in tetrahydrofuran (THF) solution, the reaction of 1 with the diols 2 and 3 gave the open chain compounds N₃P₃Cl₅[O(CH₂)₂CMe₂OH] (4) and N₃P₃Cl₅[(OCH₂CH₂)₂OH] (5), the singly bridged compound N₃P₃Cl₅[(OCH₂)₂-CMe₂]N₃P₃Cl₅ (6), the doubly bridged compounds N₃P₃Cl₄[(OCH₂)₂CMe₂]₂N₃P₃Cl₄ (8) and N₃P₃Cl₄[(OCH₂CH₂)₂O]₂N₃P₃Cl₄ (9), and the triply bridged compounds N₃P₃Cl₃[(OCH₂)₂-CMe₂]₃N₃P₃Cl₃ (10) and N₃P₃Cl₃[(OCH₂CH₂)₂O]₃N₃P₃Cl₃ (11).

The doubly bridged derivatives were also isolated in better yields relative to earlier reports. The substituted cyclotriphosphazenes have been characterized by elemental analysis, mass spectrometry, as well as by ¹H, ³¹P, and ¹³C NMR spectroscopy. It is found that with variation of the solvent there is a decrease in the product formed by intramolecular reactions (spiro and ansa derivatives) and a concomitant increase in the amount of products formed by intermolecular reactions (singly, doubly, and triply bridged derivatives) of cyclophosphazene.