Extraction—spectrophotometric determination of traces of thallium in lead,cadmium, indium and zinc metals with tri-n-octylamine

A sensitive spectrophotometric method is described for the determination of thallium in lead, cadmium, indium and zinc metals. Optimal conditions have been established for the extraction and determination of thallium. Thallium is extracted as its bromo complex with tri-n-octylamine and then converted to an iodo complex, the absorbance of which is measured at 400 nm. As little as 1 p.p.m. of thallium in lead, cadmium and zinc metals, and 2 p.p.m. of thallium in indium metal can be determined.     

Femtosecond laser ionization of organic amines with very low ionization potentials: relatively small suppressed ionization features

We examined the femtosecond nonresonant ionization of organic amines with vertical ionization potentials as low as 5.95 eV. The quantitative evaluation of suppressed ionization relative to the single active electron approximation model was done by comparing the saturation intensity, I(sat), in experiments and theory. ADK theory was found to be useful in predicting the ionization yield in the I(sat) scale within a factor of 2, even for molecules with very low ionization potentials. The degree of suppression was, however, smaller than that of benzene. The localization of electrons on the nitrogen atom was found to affect the ionization behavior under the strong laser field. The delocalized pi electrons in benzene could not follow the laser field adiabatically, while those in localized molecular orbitals could. In addition, the growth of a tunneling barrier due to the screening effect in amines may be relatively smaller than that in benzene.     

Direct synthesis of fused indoles by gold-catalyzed cascade cyclization of diynes

A direct, concise, and atom-economical synthetic method for the generation of fused indoles, using a gold-catalyzed cascade cyclization of diynes, has been developed. The reaction gave various fused indoles, such as aryl-annulated[a]carbazoles, dihydrobenzo[g]indoles, and azepino- or oxepinoindole derivatives in good to excellent yields, through an intramolecular cascade 5-endo-dig hydroamination followed by a 6- or 7-endo-dig cycloisomerization, without producing theoretical byproduct. Three of the resulting indoles exhibited potent antifungal activities against T. mentagrophytes and T. rubrum, demonstrating the practical application of the described cascade reaction for drug discovery.     

Solubility of carbon dioxide in aqueous solutions of diisopropanolamine and methyldiethanolamine

The solubility of carbon dioxide in aqueous solutions of alkanolamines was measured by means of two experimental methods. The solubility of carbon dioxide was measured at 298 K with a static total pressure apparatus in solutions of water + diisopropanolamine (DIPA) having mass fraction of DIPA equal to 10.1%, 11.0% and 33.9%. The density of the water + DIPA solution was measured continuously during the experiments to investigate the changes in density introduced by the absorption of carbon dioxide. A correlation for the density of CO₂-loaded aqueous solutions of DIPA is presented.     

Nature of plasma-induced radicals on crosslinked methacrylic polymers studied by electron spin resonance

Plasma-induced radicals of several crosslinked methacrylic polymers such as poly(ethyleneglycol dimethacrylate) (PEDMA), poly(2-hydroxyethylmethacrylate) (PHEMA) and polymethacrylamide (PMAAm) were studied by electron spin resonance (ESR). The observed ESR spectra did not exhibit a drastic difference in the spectral feature caused by the effect of crosslinking. All the spectral features can be represented by “nine-line spectra” as a major spectral component similar to those of linear methacrylic polymers such as polymethacrylic acid (PMAA). A pronounced effect of crosslinking, however, has emerged on the specific formation in the radical structure and the stability of radicals formed, especially in PEDMA. The formation of fewer kinds of radical in PEDMA is apparently caused by the high degree of crosslinking which leads to a suppression of the occurrence of depolymerization on plasma irradiation.     

Near-infrared spectroscopy for liquids of microliter volume using capillaries with wall transmission

In the present study we propose a capillary tube method for measuring near-infrared (NIR) spectra of microliter liquid and solution samples. This method enables one to measure NIR spectra of liquids and solutions of only 2.5 microl. As an example of the capillary tube method, Fourier-transform NIR spectra of benzene were measured using a capillary tube with a diameter of 1 mm. Positions and intensities of the NIR bands in the spectra obtained by the capillary tube were almost identical to those measured using a quartz cuvette cell. Moreover, capillary NIR spectra of human blood serum obtained from a patient with backbone neoplasm were also measured. Subtraction of the NIR spectrum of water from those of human blood serum develops unambiguously some NIR bands due to blood components such as proteins and glucose. Our results suggest that capillary NIR spectroscopy will open new areas of NIR applications for small amounts of liquid and solution samples.     

Total synthesis of stevioside

Steviol 2 was transformed into stevioside 1 by applying the stereoselective methods of glycosidation.     

Hydroxy-3-Phenylcoumarins as Multitarget Compounds for Skin Aging Diseases: Synthesis,Molecular Docking and Tyrosinase,Elastase, Collagenase and Hyaluronidase Inhibition,and Sun Protection Factor

Skin aging is a progressive biological process of the human body, and it is not only time-dependent. Differently substituted 3-phenylcoumarins proved to efficiently inhibit tyrosinase. In the current work, new substitution patterns have been explored, and the biological studies were extended to other important enzymes involved in the processes of skin aging, as elastase, collagenase and hyaluronidase. From the studied series, five compounds presented inhibitory activity against tyrosinase, one compound against elastase, eight compounds against collagenase and two compounds against hyaluronidase, being five compounds dual inhibitors. The 3-(4′-Bromophenyl)-5,7-dihydroxycoumarin (1) and 3-(3′-bromophenyl)-5,7-dihydroxycoumarin (2) presented the best profiles against tyrosinase (IC₅₀ = 1.05 µM and 7.03 µM) and collagenase (IC₅₀ = 123.4 µM and 110.4 µM); the 3-(4′-bromophenyl)-6,7-dihydroxycoumarin (4) presented a good inhibition against tyrosinase and hyaluronidase; the 3-(3′-bromophenyl)-6,7-dihydroxycoumarin (5) showed an effective tyrosinase and elastase inhibition; and 6,7-dihydroxy-3-(3′-hydroxyphenyl)coumarin (11) presented a dual profile inhibition against collagenase and hyaluronidase. Furthermore, considering the overall activities tested, compounds 1 and 2 proved to be the most promising anti-aging compounds. These compounds also showed to have a photo-protective effect, without being cytotoxic to human skin keratinocyte cells. To predict the binding site with the target enzymes, computational studies were also carried out.     

Bis-phosphoryl-bridged stilbenes synthesized by an intramolecular cascade cyclization

Bis-phosphoryl-bridged stilbenes have been synthesized using an intramolecular cascade cyclization. They show intense blue fluorescences at longer wavelengths with higher quantum yields compared to those of the known element-bridged stilbenes. In addition, they have much lower reduction potentials due to the inductive effect of phosphoryl groups. The incorporation of the phosphoryl moiety is an effective way for the construction of highly electron-accepting pi-conjugated systems.