Synthesis of novel deoxynucleoside S-methylphosphonic acids using S-(diisopropylphosphonomethyl)isothiouronium tosylate, a new equivalent of mercaptomethylphosphonate

The synthesis of the novel nucleotide analogues 5'-deoxynucleoside-5'-S-methylphosphonates, starting from 5'-deoxy-5'-haloribonucleosides, 5'-O-tosylribonucleosides, and 2'-O-triflylnucleosides, is described. The phosphonothiolation of these compounds was achieved using S-(diisopropylphosphonomethyl)isothiouronium tosylate, a new, odourless, and efficient equivalent of mercaptomethylphosphonate. The thiolate anion of mercaptomethylphosphonate was generated in situ from the isothiouronium salt in both protic and aprotic solvents using two equivalents of sodium iso-propoxide. The prepared nucleoside 5'-S-methylphosphonates were deprotected, and the free phosphonic acids were transformed into diphosphoryl derivatives (the NTP analogues). Both mononucleotides and NTP analogues were studied as substrates/inhibitors of several enzymes that are involved in the nucleoside/nucleotide metabolism.     

About mechanism of foam stabilization by solid particles

The main objective of the research was to study the properties of the foam and foam films stabilized by solid particles. The properties of the foam films were compared with the analogous ones of the emulsion films. The experiment provided the rheological characteristics of the dispersion medium. The research provided the study of the correlation of the contact angle, the shear stress, the surface tension and the radii of aggregates by the solid particles and the modifier concentration. The effect of the foam film stabilization by the solid particles is significant.     

Noble metals in polyoxometalate chemistry: palladium-containing derivatives of the monolacunary Keggin and Wells-Dawson tungstophosphates

We have prepared the three novel Pd(II)-containing tungstophosphates [Pd(2)(α-PW(11)O(39)H(0.5))(2)](9-) and two structural isomers of [Pd(2)(α(2)-P(2)W(17)O(61)H(n))(2)]((16-2n)-) via simple synthetic procedures and characterized their potassium salts by single-crystal X-ray diffraction, elemental analysis, and IR and multinuclear ((31)P and (183)W) NMR spectroscopy. This study sheds light on the long-standing question about the nature and structure of the actual products formed in the reaction of Pd(II) ions with monolacunary Keggin-type [α-XW(11)O(39)](n-) and Wells-Dawson-type [α(2)-P(2)W(17)O(61)](10-) heteropolytungstates.     

Synthesis and reactivity of cinnoline-fused cyclic enediyne

A short and efficient synthesis of cinnoline-fused cyclic enediyne is reported. Richter cyclization of o-(1,3-butadiynyl)phenyltriazene produced 3-alkynyl-4-bromocinnoline. The Sonogashira coupling of the latter with 5-hexyn-1-ol was employed for the introduction of a second acetylenic moiety. The crucial cyclization step was achieved under Nozaki-Hiyama-Kishi conditions. Cinnoline-fused 10-membered ring enediyne is more reactive than corresponding carbocyclic analog and produces good yield of the Bergman cyclization product upon mild heating. This enediyne induces single-strand dDNA scissions upon incubation at 40 °C.     

Visualization of type II fiber Bragg gratings induced in a birefringent fiber with an elliptical stress cladding

Experimental results on visualization of type II fiber Bragg gratings induced in a birefringent fiber with an elliptical stress cladding are presented. The gratings are recorded by a single pulse of an excimer KrF-laser by means of the phase-mask method. Images of the gratings are obtained in a bright field using contrasting techniques such as differential interference contrast and dark field. It is shown that single-pulse recording forms several type II Bragg gratings in the optical fiber. The spatial profile of these gratings corresponds to the phase mask period. Microcracks due to which type II gratings are induced are localized both on the boundaries between the fiber core and claddings surrounding it and at some distance from them.     

Volatile Organic Compound Fragmentation in the Afterglow of Pulsed Glow Discharge in Ambient Air

Glow discharge (GD) source gained an increased level of attention in relation to the analysis of volatile organic compounds (VOCs) since past work showed that this soft ionization method allowed direct analysis of VOCs with minimal fragmentation, however, the issue of fragmentation was not previously studied in detail. The aim of the present work was to investigate the effect of discharge conditions on VOC fragmentation in the system consisting of the cell with pulsed glow discharge and a time-of-flight mass spectrometer. Ionization of VOCs of different classes (hydrocarbons, alcohols, esters, and carboxylic acids) was investigated. A copper cathode with flat geometry was used. VOCs were ionized in the afterglow of short pulse glow discharge in the air. The use of discharge afterglow significantly reduces or eliminates the effects of ionization mechanisms other than Penning process, in particular, electron ionization. This significantly reduced VOC fragmentation and provided rather low limits of detection. Specific cluster formation was observed for alcohols and esters, which may facilitate their identification.     

An Efficient Method of Birch Ethanol Lignin Sulfation with a Sulfaic Acid-Urea Mixture

For the first time, the process of birch ethanol lignin sulfation with a sulfamic acid-urea mixture in a 1,4-dioxane medium was optimized experimentally and numerically. The high yield of the sulfated ethanol lignin (more than 96%) and containing 7.1 and 7.9 wt % of sulfur was produced at process temperatures of 80 and 90 °C for 3 h. The sample with the highest sulfur content (8.1 wt %) was obtained at a temperature of 100 °C for 2 h. The structure and molecular weight distribution of the sulfated birch ethanol lignin was established by FTIR, 2D ¹H and ¹³C NMR spectroscopy, and gel permeation chromatography. The introduction of sulfate groups into the lignin structure was confirmed by FTIR by the appearance of absorption bands characteristic of the vibrations of sulfate group bonds. According to 2D NMR spectroscopy data, both the alcohol and phenolic hydroxyl groups of the ethanol lignin were subjected to sulfation. The sulfated birch ethanol lignin with a weight average molecular weight of 7.6 kDa and a polydispersity index of 1.81 was obtained under the optimum process conditions. Differences in the structure of the phenylpropane units of birch ethanol lignin (syringyl-type predominates) and abies ethanol lignin (guaiacyl-type predominates) was manifested in the fact that the sulfation of the former proceeds more completely at moderate temperatures than the latter. In contrast to sulfated abies ethanol lignin, the sulfated birch ethanol lignin had a bimodal and wider molecular weight distribution, as well as less thermal stability. The introduction of sulfate groups into ethanol lignin reduced its thermal stability.     

Conformational polymorphs of 3‐cyclopropyl‐5‐(3‐methyl‐[1,2,4]triazolo[4,3‐a]pyridin‐7‐yl)‐1,2,4‐oxadiazole

The dipharmacophore compound 3‐cyclopropyl‐5‐(3‐methyl‐[1,2,4]triazolo[4,3‐a]pyridin‐7‐yl)‐1,2,4‐oxadiazole, C₁₂H₁₁N₅O, was studied on the assumption of its potential biological activity. Two polymorphic forms differ in both their molecular and crystal structures. The monoclinic polymorphic form was crystallized from more volatile solvents and contains a conformer with a higher relative energy. The basic molecule forms an abundance of interactions with relatively close energies. The orthorhombic polymorph was crystallized very slowly from isoamyl alcohol and contains a conformer with a much lower energy. The basic molecule forms two strong interactions and a large number of weak interactions. Stacking interactions of the `head‐to‐head' type in the monoclinic structure and of the `head‐to‐tail' type in the orthorhombic structure proved to be the strongest and form stacked columns in the two polymorphs. The main structural motif of the monoclinic structure is a double column where two stacked columns interact through weak C—H…N hydrogen bonds and dispersive interactions. In the orthorhombic structure, a single stacked column is the main structural motif. Periodic calculations confirmed that the orthorhombic structure obtained by slow evaporation has a lower lattice energy (0.97 kcal mol^?1) compared to the monoclinic structure.     

New flavonoid-containing derivatives of lupinine

An oxazine ring was annelated to benzopyran-4-one and benzopyran-2-one cores by reacting 7-hydroxyisoflavones and 7-hydroxycoumarins with lupinylamine and formalin. The new derivatives 9,10-dihydro4H,8 H-chromeno[8,7-e][1,3]oxazin-4-one and 9,10-dihydro-2 H,8 H-chromeno[8,7-e][1,3]oxazin-2-one containing a lupinine moiety in the 9-position were prepared.