Synthesis and reduction of some 1H-2,1,3-benzothiadiazin-4(3H) one 2,2-dioxides

Several 2,1,3-benzothiadiazin-4(3H) one 2,2-dioxides were synthesized as possible sweetening agents by reacting sulfamoyl chloride with various anthranilic acid derivatives. The isolation of 1-methyl-4-methoxy-2,1,3-benzothiadiazine 2,2-dioxide and preparation of 3,4-dihydro-2,1,3-benzothiadiazine 2,2-dioxide is also reported.     

Mercury Speciation in Fish by High-Performance Liquid Chromatography (HPLC) and Post-Column Ultraviolet (UV)-Photochemical Vapor Generation (PVG): Comparison of Conventional Line-Source and High-Resolution Continuum Source (HR-CS) Atomic Absorption Spectrometry (AAS)

An ultraviolet-photochemical generator (UV-PVG) capable of post-column on-line transformation of both organic and inorganic mercury species to cold vapor (Hg⁰) with subsequent detection by quartz tube-atomic absorption spectrometry (QT-AAS) was developed. Mercury(II), methylmercury(I), ethylmercury(I), and phenylmercury(I) were successfully detected after separation by reversed-phase high-performance liquid chromatography (RP-HPLC). Two types of AAS detectors were compared. The first was a commonly used line-source instrument while the second was a high-resolution continuum source (HR-CS) AAS. The latter provided better limits of detection: 0.47?µg?L^?1 for Hg(II), 0.84?µg?L^?1 for methylmercury(I), 0.80?µg?L^?1 for ethylmercury(I), and 2.0?µg?L^?1 for phenylmercury(I). The repeatability at 30?μg?L^?1 was 3.6%, 4.1%, 6.2%, and 4.5% for these species (n?=?10). These figures of merit were comparable with those reported for more sensitive atomic fluorescence spectrometry. Nine sample extraction procedures were investigated. Extraction by tetramethylammonium hydroxide and HCl at 75?°C was selected as the only method compatible with the proposed separation and detection steps providing high extraction efficiency and no changes in mercury speciation. The applicability of the proposed high-performance liquid chromatography–ultraviolet-photochemical vapor generation–quartz tube-atomic absorption spectrometry method was demonstrated using fish samples and certified reference materials (CRM) DOLT-4 (dogfish liver) and ERM-CE464 (tuna fish). The results were comparable to those obtained by a reference method based on L-cysteine extraction and high-performance liquid chromatography–inductively coupled plasma-mass spectrometry (HPLC–ICP-MS) determination.     

Influence of substitutions on asymmetric dihydroxychlorins with regard to intracellular uptake, subcellular localization and photosensitization of Jurkat cells

The search for new efficient sensitizers for photodynamic therapy (PDT) points to improve photophysical properties like absorption in the red region and singlet oxygen quantum yield as well as to control the localization of the sensitizer within the tumour cell. Depending on their physicochemical properties and their uptake mechanism, sensitizers can reach different intracellular concentrations and localize in different subcellular compartments. Moreover, the preferential localization of a sensitizer in target organelles, like mitochondria or lysosomes, could determine the cell death mechanism after PDT. This study aimed to investigate the influence of substitutions on dihydroxychlorins with regard to intracellular uptake, subcellular localization and cell death pathway. Moreover, the effect of a liposome-based delivery system was tested. The intracellular uptake was found to be strictly dependent on the sensitizer molecular structure and the means of its delivery. The most polar sensitizer in this study (compound 3) had, depending on incubation time, an intracellular concentration 2-8 times higher than the unsubstituted chlorin 1. All investigated photosensitizers localize predominantly in lysosomes but after longer incubation times weak fluorescence intensity was also detected in mitochondria and Golgi apparatus. The cell death pathway was found to be influenced by the sensitizer intracellular concentration and the applied light doses. In general, the increasing amphiphilicity of the sensitizer molecules is correlated with an increased sensitizer uptake and an increased rate of necrotic cells after irradiation.     

Analysis of Mepivacaine in Human Serum by Gas Chromatography After Solid-Phase Extraction

A method using solid-phase extraction (SPE) has been developed for analysis of mepivacaine in human serum. A procedure for isolation of mepivacaine and lidocaine (internal standard) from human serum by use of Chromosorb 104 (acrylonitrile–divinylbenzene polymer) as extraction adsorbent is described in detail. Analysis was performed by gas chromatography on an HP-INNOWax (cross-linked PEG) capillary column, with flame ionization detection, after splitless injection. Relative standard deviations ranged between 3.6 and 4.4 for a serum mepivacaine concentration of 0.5 g mL^–1 and between 4.7 and 5.9 for a concentration of 1 g mL^–1. Recoveries were approximately 95%. The method was applied in a stomatological clinic to healthy volunteers to whom anesthesia with mepivacaine was administered.     

Molten sodium nitrite—potassium nitrite eutectic: the reaction of some compounds of molybdenum

Molybdenum(VI) oxide, ammonium molybdate and molybdic acid reacted in molten sodium nitrite—potassium nitrite eutectic to form orthomolybdate, nitrogen dioxide and nitric oxide (with nitrate as a secondary product), a more polymerised polymolybdate being formed as an intermediate product. Tungsten(VI) oxide reacted similarly but less rapidly. Molybdenum and tungsten metals reacted to form the orthoxyanion and nitrogen, the latter metal reacting considerably faster and forming smaller amounts of nitric oxide and nitrous oxide. Reaction temperatures and stoichiometries are given and reaction pathways suggested.     

Factors Contributing to Solubility Synergism of Some Basic Drugs with β-Cyclodextrin in Ternary Molecular Complexes

Ternary complexes exploiting solubility synergism (SSn) between basic drugs and β-cyclodextrin (β-CD) in the presence of an organic hydoxy acid have been reported to provide the pharmaceutical technology with highly soluble ternary complexes, even with the least soluble β-CD. In this work, phase solubility techniques were used to study factors affecting SSn in aqueous solution, which may help in understanding the mechanism involved in ternary complex formation in solution, under equilibrium conditions. The equilibrium solubility of both β-CD and each of 8 structurally unrelated drugs were measured in tandem in the presence of different acid types at low and high pHs, and at different time intervals over a period of 1–40 days. The results indicate that SSn is evident regardless of acid type (organic and inorganic) at low pH, but the extent of SSn is acid type dependant and is limited by the drug salt solubility product constant (pK _sp). Among different drugs, no apparent trend exists between drug salt solubility and the extent of SSn, but lowering drug salt solubility by increasing pH depresses SSn. The results also reveal no apparent trend between the magnitude of the complex formation constant (K _ij) and SSn. For example, drugs of low K _ij values such as astemizole, cisapride and sildenafil do not show any SSn, yet ketotifen and pizotifen, which also have low K _ij values, exhibit substantial SSn. However, the solublizing power of β-CD represented by the slope of phase solubility diagram can be used as a marker for SSn (slopes exceeding 0.4 induce SSn).     

Novel vinyl phosphonates and vinyl boronates by halogenation, allylation, and propargylation of alpha-boryl- and alpha-phosphonozirconacyclopentenes

[structure: see text] Alpha-phosphonozirconacyclopentenes or alpha-borylzirconacyclopentenes react by bromination, iodination, allylation, and propargylation to generate unique vinyl boronates and vinyl phosphonates not obtainable by other methods. The reaction proceeds in two steps, with both high regio- and stereoselectivity. With the vinyl boronates, the Zr-Csp2 bond is initially cleaved by 1 equiv of electrophile. With the phosphonates, either the Zr-Csp2 bond (allyl bromide, Br(2)) or the Zr-Csp3 bond (I(2), propargyl bromide) may be initially cleaved. The addition of a second equivalent of an electrophile results in disubstitution.     

The synthesis of single enantiomers of meromycolic acids from mycobacterial wax esters

Three stereoisomers of a wax ester meromycolate have been prepared starting from mannitol. A detailed comparison of their NMR spectra with those reported for a homologous series of natural wax esters allows the relative configurations of the α-methyl group and adjacent trans-cyclopropane to be determined.     

Sulfonic cation exchangers based on immobilized cis-Calix[4]resorcinolarenes

New sulfonic cation exchangers based on immobilized calix[4]resorcinolarenes were prepared. Their ion-exchange properties toward Na⁺, Cu²⁺, [Pd(NH₃)₄]²⁺, In³⁺, and Sn⁴⁺ ions were studied in a wide pH range, and their chemical stability was examined.     

Methods for producing 195m Pt isomer

Among nuclides, ^195m Pt isomer is characterized by a number of properties that make it suitable for use in nuclear medicine. Effective ways of optimizing the Pt isomer yield at low impurity contents must be sought. The method based on double neutron capture by the ¹⁹³Ir target nucleus with subsequent populating of ^195m Pt through β decay allows chemical isolation of the isomer. In this work, the problem is analyzed, test experiments on Ir activation with neutrons are conducted, and theoretical estimates of the ^195m Pt yield are presented. Full-scale model experiments on the IBR-2 reactor in Dubna should confirm the effectiveness of the method.