New phosphonic analogs of aspartic and glutamic acid by aminoalkylation of trivalent phosphorus chlorides with ethyl acetyloacetate or ethyl levulinate and benzyl carbamate

Preparation of the phosphonic analogs of -methylaspartic (4 a–d), glutamic (7 a–b) and -methylpyroglutamic (5 a–b) acids by aminoalkylation of trivalent phosphorus chlorides with ethyl esters of oxoalkyloacids and benzyl carbamate is described. The phosphonic analogs of pyroglutamic acid (8 a–b) was obtained by the cyclization of the corresponding esters (9 a–b). The stability of the phosphonic analogs of pyroglutamic acid in acidic and alkaline media was also studied.

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Die Herstellung von neuen Phosphonanalogen der Asparagin- und Glutaminsäure in der Reaktion von trivalenten Phosphorchloriden mit Ethyl-acetyloacetat oder Ethyl-lävulinat bzw. Benzylcarbaminat

Zusammenfassung Es wurde die Darstellung der Phosphonanalogen der -Methylasparaginsäure (4 a–d), Glutamin- (7 a–b) und -Methylpyroglutaminsäure (5 a–b) in der Reaktion der trivalenten Phosphorchloride und der Oxoalkansäureethylester sowie des Benzylcarbaminats beschrieben. In der Ringschlußreaktion der Ester (9 a–b) erhält man Phosphonanaloge der Pyroglutaminsäure. Die Stabilität der Analogen der Pyroglutaminsäure wurde in sauren und alkalischen Medien geprüft.

     

Mechanistic Study on the Oxidation of Promazine and Chlorpromazine by Hexaimidazolcobalt(III) in Acidic Aqueous Media

The kinetics of the oxidation of promazine and chlorpromazine by hexaimidazolcobalt(III) were studied in the presence of a large excess of cobalt(III) and H⁺ ions using u.v.–vis. spectroscopy ([Co^III] = (1–6) × 10⁻³ m, [ptz] = (2.5–10) × 10⁻⁵ m, [H⁺] = 0.05–0.8 m, I = 1.0 m (H⁺, Na⁺, Cl⁻), T = 333–353 K, l = 1 cm). In each case, the reversible reaction leads to formation of cobalt(II) species and a stable cationic radical. A linear dependence of the pseudo-first-order rate constant (k_obs) on [Co^III] with a non-zero intercept was established for both phenothiazine derivatives. A marked difference in the observed reaction rate for promazine and chlorpromazine is associated with the difference in its ability to undergo oxidation and is consistent with a trend in the redox potential changes for these reductants. The activation parameters for reactions studied were determined. Mechanistic consequences of all the results are discussed.     

The first example of Diels-Alder cycloaddition of ortho-xylylenes to meso-tetraarylporphyrins containing electron-deficient β,β-double bonds

β-Nitro-5,10,15,20-tetraphenylporphyrin and its zinc complex, or 2,7-dinitro-5,10,15,20-tetraphenylporphyrin, react with 1,3-dihydrobenzo[c]thiophene 2,2-dioxide in refluxing 1,2,4-trichlorobenzene, giving rise to chlorins, bacteriochlorins or isobacteriochlorins. The products obtained are attractive intermediates for further functionalization of porphyrins and may be of potential use as sensitizers in photodynamic therapy.     

Kinetics and mechanism of a trans-tetraazamacrocyclic chromium(III) complex oxidation by hexacyanoferrate(III) in strongly alkaline media

Oxidation of the trans-[Cr(cyca)(OH)₂]⁺ complex, where cyca = meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, by [Fe(CN)₆ ]^3- ion in strongly alkaline media, leading to [Cr^V O(cyca_ox )]³⁺ ion, has been studied using electronic and e.p.r. spectroscopy. The kinetics of the Cr^III → Cr^IV transformation have been studied using a large excess of the reductant and OH^- ion over the oxidant. The reaction is a second order process: first order in [Cr^III] and [Fe^III] at constant [OH^-]. The second order rate constant is higher than linearly dependent on the OH^- concentration. The mechanism of the reaction has been discussed. A relatively inert intermediate chromium(V) species was detected based on characteristic bands in the visible region and the e.p.r. signal at g_iso = 1.987 for the systems where an excess of oxidant was used. The hyperfine structure of the main e.p.r. signal is consistent with the d¹ -electron interactions with four equivalent nitrogen nuclei and [Cr^V = O(cyca_ox)]³⁺ formula, where cyca_ox = oxidized cyca, can be postulated for the intermediate Cr^V complex.     

Betaine and Carnitine Derivatives as Herbicidal Ionic Liquids

This study focused on the synthesis and subsequent characterization of herbicidal ionic liquids based on betaine and carnitine, two derivatives of amino acids, which were used as cations. Four commonly used herbicides (2,4‐D, MCPA, MCPP and Dicamba) were used as anions in simple (single anion) and oligomeric (two anions) salts. The obtained salts were subjected to analyzes regarding physicochemical properties (density, viscosity, refractive index, thermal decomposition profiles and solubility) as well as evaluation of their herbicidal activity under greenhouse and field conditions, toxicity towards rats and biodegradability. The obtained results suggest that the synthesized herbicidal ionic liquids displayed low toxicity (classified as category 4 compounds) and showed similar or improved efficacy against weed compared to reference herbicides. The highest increase was observed during field trials for salts containing 2,4‐D as the anion, which also exhibited the highest biodegradability (>75 %).     

The DSC approach to study non-freezing water contents of hydrated hydroxypropylcellulose (HPC)

Journal of Thermal Analysis and Calorimetry - The research consisted of investigation of non-freezable bound water (NFW) contents of raw hydroxypropylcellulose (HPC) Klucel® Pharm HF, MF, and...     

Frequency aspects of the THz photomixer

In the paper methods of the terahertz photomixer operational frequency estimation are considered. Three methods are investigated — estimation of the frequency via direct measurements of the laser heterodyne compounds, via calculations from datasheets, and via calculations from raw collected data obtained from the photomixer system.     

Adsorption of Ni(II) from model solutions using co-precipitated inorganic oxides

The aim of this work was to obtain an inorganic oxide system containing silica and magnesium oxide, and characterized by specific physicochemical properties, in particular well-defined adsorption parameters. The preparation process was carried out according to a co-precipitation method using solutions of sodium silicate and selected inorganic magnesium salt. The oxide system obtained (MgO·SiO₂) was used as a support (adsorbent) of nickel(II) ions, whose precursors were model solutions of nitrates. The effectiveness of the adsorption process was evaluated using many different analytical techniques, including atomic absorption spectroscopy, energy dispersive X-ray spectroscopy and equivalent point titration. Moreover the stability of adsorbent/adsorbate bonding was estimated. The oxide systems—adsorbents—used in the process were also analyzed according to their physicochemical properties, especially changes in adsorption parameters. The last part of the study involved evaluation of the kinetics of the adsorption process depending on time and the pH of the reaction system.     

Labelling of peptides with <Superscript>99m</Superscript>Tc complexes through the modified C-terminal group

Easy and efficient way to modify of the C-terminus of the peptide using amino acid lysine has been proposed and experimentally verified. The synthesis yield was high (≥85%) and it was found that reactions can be carried out even with microgram amounts of the peptide. Using Fmoc-alanine (as the peptide model) with modified C-terminus the procedure of peptide labelling with monovalent and trivalent ^99mTc complexes has been elaborated.     

Two-electron entanglement in elliptically deformed quantum dots

Entropic entanglement measures of a two-dimensional system of two Coulombically interacting particles confined in an anisotropic harmonic potential are discussed in dependence on the anisotropy and the interaction strength. The harmonic approximation appears exact in the strong interaction limit, allowing determination of the asymptotic expression for the linear entropy. Entanglement properties are dramatically influenced by the anisotropy of the confining potential in the strong-correlation regime.