Showing papers in "Russian Journal of General Chemistry in 2015"
TL;DR: In this article, the results of investigations of low-current discharges in a gas flow at atmospheric pressure are described, where glow discharges are typically used for obtaining a plasma jet at the exit of the electrode system.
Abstract: The paper describes the results of investigations of low-current discharges in a gas flow at atmospheric pressure. The primary focus is on glow discharges in coaxial plasmatrons and the so-called gliding arc. Such discharges are typically used for obtaining a plasma jet at the exit of the electrode system. The jet contains active chemical species playing an important role in various applications of the discharge. Plasma-assisted combustion and oxidation of hydrocarbon fuels is also considered. Besides, the applications of plasma jet for modification of surfaces and for use in biology and medicine are discussed.
47 citations
TL;DR: In this paper, the structure and specific features of isocyanide palladium(II) complexes with mono-and polynitrogen nucleophiles, as well as the structure of the products of these transformations, are discussed.
Abstract: The review generalizes published data on the chemistry of palladium(II) complexes with isocyanides. The structure and specific features of the reactivity of isocyanide palladium(II) complexes with mono- and polynitrogen nucleophiles, as well as the structure of the products of these transformations, are discussed.
41 citations
TL;DR: In this article, the complexation effect of selected ligands on the redox potential of iron, cobalt and copper redox couples is studied. And the application of coordination modulated redox properties in the natural attenuation of toxic environmental contaminants is also presented.
Abstract: Ligand effect is a favorable factor in modulation of redox potential of transition metal ion oxidation-reduction systems. Coordination promoted redox action of transition metals can be an efficient approach to design of new redox systems with specific applications. The current review is devoted to the complexation effect of selected ligands on the redox potential of iron, cobalt and copper redox couples and application of such systems in analytical estimations. Indirect estimation of non redox systems by a non redox reaction over a platinum electrode has been referred to as a pseudo indicator action. Application of coordination modulated redox potentials in the natural attenuation of toxic environmental contaminants is also presented.
40 citations
TL;DR: In this article, the principles of generating low temperature capacitively coupled in a vacuum chamber of a large size with the use of original low-pressure arc discharges are considered, and the designs of plasma sources and their main parameters are described.
Abstract: In the paper the principles of generation of low temperature capacitively coupled in a vacuum chamber of a large size with the use of original low-pressure arc discharges are considered. The designs of plasma sources and their main parameters are described. Examples of effective use of the generated plasma in plasma chemical modification of the surfaces of materials and products are presented.
37 citations
TL;DR: A series of azomethine precursors were derived by the condensation of 4H-1,2,4-triazole-4-amine with salicylaldehyde.
Abstract: A series of novel azomethine precursors were derivatized by the condensation of 4H-1,2,4-triazole-4-amine with salicylaldehyde (HL
1) (saltrz), 2,3-dihydroxybenzaldehyde (HL
2) (dhtrz), 2-hydroxy-1-naphthaldehyde (HL
3) (ndtrz) and 5-chloro-2-hydroxybenzaldehyde (HL
4) (cltrz). Subsequently, oxovanadium(IV) complexes of the type [VO(saltrz)2] (1), [VO(dhtrz)2] (2), [VO(ndtrz)2] (3), and [VO(cltrz)2] (4) were synthesized by the reactions of vanadyl(V) isopropoxide [VO(OCHMe2)3] with the ligands HL
1–HL
4. The synthesized compounds were characterized by the melting point method, elemental analysis, FT-IR and 1H and 13C NMR spectroscopies, the molar susceptibility and conductivity methods, and by the thermogravimetry. Ligands HL
3 and HL
4 were also characterized by single crystal analysis. The binding modes of SS-DNA with the compounds were confirmed by the hypochromism and red/blue shift of the UV-Vis spectra. The negative DG values of the compound-DNA adducts show that the binding is a spontaneous process. The complexes were found to be persuasive inhibitors of enzyme alkaline phosphatase (ALP). The in vitro screening of the antimicrobial activities of the synthesized compounds revealed significantly enhanced activities of oxovanadium(IV) complexes as compared to their respective ligands. The promising results were obtained in studying the insulin mimetic of the synthesized compounds.
30 citations
TL;DR: Theoretical and practical results of the treatment of water and aqueous solutions by low-temperature nonequilibrium contact plasma are considered in this article, where it is shown that the liquid medium in the process of plasma treatment or thereafter undergoes significant structural and physical-chemical transformations, the use of which opens up new horizons in the modernization or improvement of technological processes to replace out-of-date or obsolete ones.
Abstract: Theoretical and practical results of the treatment of water and aqueous solutions by low-temperature nonequilibrium contact plasma are considered. It is shown that the liquid medium in the process of plasma treatment or thereafter undergoes significant structural and physical-chemical transformations, the use of which opens up new horizons in the modernization or improvement of technological processes to replace out-of-dated or obsolete ones.
27 citations
TL;DR: In this article, new effective photosensitizers absorbing in the long-wave spectral region were revealed, including Alasens-lio, Alasensgel, Hexasens-Lia, Phthalosens-LOI, HolosensLOI and HolosENSgel.
Abstract: Photodynamic therapy and fluorescence diagnosis of malignant tumors have been actively developed over the last 15 years by the scientists participating in the Moscow Government-funded “Fight against Cancer” program. New effective photosensitizers absorbing in the long-wave spectral region were revealed. Unique agents Alasens-lio, Alasens-gel, Hexasens-lio, Phthalosens-lio, Holosens-lio, and Holosensgel were produced and preclinically studied both in vitro and in vivo. New methods using low-intensity and pulse modes of irradiation and also combined methods of treatment by photodynamic therapy and well-known chemotherapy or laser hyperthermia were developed. Methodological recommendations for experimental studies of agents with photoinduced antitumor properties were published.
25 citations
Abstract: Triethanolammonium salts (protatranes) of biologically active carboxylic acids (nicotinic, cinnamic, benzoic, salicylic, oxalic, malonic, succinic, malic, citric) were synthesized in yields exceeding 90%. The structure of the synthesized compounds was studied by IR spectroscopy and X-ray diffraction analysis.
22 citations
TL;DR: It was shown that photodynamic therapy is effective for adjuvant or intraoperative treatment in patients with high risk of local recurrence after surgical treatment, and palliative photodynamic Therapy increases the quality of life and survival rates in the most challenging group of cancer patients.
Abstract: The main steps of development of fluorescence diagnosis and photodynamic therapy were overviewed. Brief historical data were presented about Photohem, Photosens, Alasens, Radachlorin, and Photoditazine photosensitizers, along with their corresponding pharmacokinetic properties, mechanisms of action, and specific features of use. Key aspects of development of fluorescence diagnosis and photodynamic therapy in Gertsen Moscow Research Oncological Institute were described. The main indications for photodynamic therapy and its efficiency in patients with oral, tongue, stomach, esophageal, skin, cervical, and central lung cancer and vulval lesions were demonstrated. It was shown that photodynamic therapy is effective for adjuvant or intraoperative treatment in patients with high risk of local recurrence after surgical treatment, and palliative photodynamic therapy increases the quality of life and survival rates in the most challenging group of cancer patients. The results of photodynamic therapy for cervical pre-cancer and cancer associated with human papillomavirus were reported. The main trends of intraoperative “fluorescence guidance” with Alasens were covered. Clinical experience allows rating photodynamic therapy among the most encouraging methods for the current medicine.
22 citations
TL;DR: In this paper, a series of transition metal complexes of Mn(II), Fe(III), Co(III) Co(II, Ni(II) Ni(I), Cu(I) and Sb(III ) containing the bidentate Schiff base derived from condensation of S-methyldithiocarbazate and cinnamaldehyde were synthesized and characterized by IR, 1H NMR, UV-Vis, and some physical measurements.
Abstract: A novel series of transition metal complexes of Mn(II), Fe(III) Co(II), Ni(II), Cu(II), and Sb(III) containing the bidentate Schiff base derived from condensation of S-methyldithiocarbazate and cinnamaldehyde were synthesized and characterized by IR, 1H NMR, UV-Vis, and some physical measurements. IR spectral studies indicated the binding sites of the Schiff base ligand with the metal ions. Molar conductance data and magnetic susceptibility measurements indicated monomeric and neutral nature of the complexes. The complexes demonstrated moderate to strong antimicrobial activity.
21 citations
TL;DR: In this article, a novel bidentate Schiff base containing NS donor sequences was synthesized by condensing S-methyldithiocarbazate (SMDTC) with p-anisaldehyde.
Abstract: A novel bidentate Schiff base containing NS donor sequences was synthesized by condensing S-methyldithiocarbazate (SMDTC) with p-anisaldehyde. A series of complexes of the ligand with Cu(II), Ni(II), Zn(II), Pb(II), Co(II), Mn(II) and U(VI) were studied and characterized by various physico-chemical methods. Cu(II), Ni(II) and Zn(II), Pb(II) complexes were four-coordinate with square plannar and tetrahedral geometry respectively. Co(II), Mn(II), and U(VI) complexes were six-coordinate with octahedral geometry. Antimicrobial activity of the prepared complexes was tested as resistance to antimicrobial agents in a wide variety of nosocomial and community-acquired pathogens. The highest antimicrobial activity was detected for the complex Co(II) against candida species.
TL;DR: In this article, the formation of nanocrystalline yttrium orthoferrite of ∼30 nm average crystallite size from coprecipitated iron(III) and Yttrium hydroxides was studied by thermo-X-ray diffractometry and simultaneous thermal analysis over 25-900°C temperature range.
Abstract: Formation of nanocrystalline yttrium orthoferrite of ∼30 nm average crystallite size from coprecipitated iron(III) and yttrium hydroxides was studied by thermo-X-ray diffractometry and simultaneous thermal analysis over 25–900°C temperature range. A mechanism of physicochemical transformations leading to the formation of YFeO3 nanoparticles was suggested.
TL;DR: A review of studies on the synthesis and modification of nanosized particles by electrical discharges in liquid media is presented in this article, where the modern understanding of the mechanisms of initiation and features of discharge evolution in liquids are analyzed.
Abstract: A review of studies on the synthesis and modification of nanosized particles by electrical discharges in liquid media is presented. The modern understanding of the mechanisms of initiation and features of discharge evolution in liquids are analyzed. By using of the spectroscopic diagnostics, parameters of the discharge plasma in liquids (water, ethanol) are determined. It is shown that the pulsed electrical discharge between electrodes immersed in a nonconducting or weakly conducting liquid, provides a simple and effective method for the synthesis of nanoparticles of different compositions with the average size ranging from 5 to 50 nm. The morphology, phase structure, and composition of the particles formed are defined by the discharge mode and composition of the liquid medium in which the discharge is produced. The conditions for the synthesis of nanosized metal oxides, carbides, and silicides (for example, copper and zinc oxides, titanium and tungsten carbides, gadolinium silicides) were found. Zinc oxide nanoparticles were produced in pulsed electrical discharge plasma in distilled water, and the possibility of their doping with nitrogen atoms during synthesis was demonstrated. Experimental results on the modification of tungsten and copper powders by spark discharge in ethanol are discussed. The possibility to synthesize copper chalcogenides CuInSe2 by electrical discharge treatment of a mixture of copper, indium, and selenium powders was demonstrated.
TL;DR: A series of linear tetrapeptides and macrocyclic pentapeptides have been synthesized starting with N,N-bis(1-carboxy-2-substituted)-3,5-diaminocarbonyl)pyridine as discussed by the authors.
Abstract: A series of linear tetrapeptides and macrocyclic pentapeptides has been synthesized starting with N,N-bis(1-carboxy-2-substituted)-3,5-diaminocarbonyl)pyridine and N,N-bis(1-hydrazonyl-2-substituted)-3,5-diaminocarbonyl)pyridine. Structures of newly synthesized compounds were elucidated by IR, 1H and 13C NMR, and MS spectral data and elemental analysis.
TL;DR: In this article, the Southern Scientific Center, Russian Academy of Sciences, ul. Chekhova 41, Rostov-on-Don, 344006 Russia e-mail: mikhail@ipoc.rsu.ru
Abstract: a Southern Scientific Center, Russian Academy of Sciences, ul. Chekhova 41, Rostov-on-Don, 344006 Russia e-mail: mikhail@ipoc.rsu.ru b Southern Federal University, Rostov-on-Don, Russia c Institute of Arid Zones, Southern Scientific Centre, Russian Academy of Sciences, Rostov-on-Don, Russia d Scientific Research Institute of Physical and Organic Chemistry, Southern Federal University, Rostov-on-Don, Russia
TL;DR: In this paper, a series of tetrapeptide Schiff bases and a macrocyclic pentapeptide were synthesized using Nα-dinicotinoyl-bis[L-leucyl-L-phenylalaninyl acid hydrazide] derivative and macro-cyclic Pentapeptides ester as starting materials and were screened for antimicrobial activity.
Abstract: A series of tetrapeptide Schiff bases and a macrocyclic pentapeptide were synthesized using Nα-dinicotinoyl-bis[L-leucyl-L-phenylalaninyl acid hydrazide] derivative and macrocyclic pentapeptide ester as starting materials and were screened for antimicrobial activity. Some of the newly synthesized compounds exhibited better antimicrobial effect compared to the reference controls. The structures of the newly synthesized compounds were confirmed by IR, NMR, and mass spectral data and elemental analyses.
TL;DR: In this paper, reaction of N-arylacetoacetamides with aromatic aldehydes in the presence of piperidine in ethanol afforded N,N′,2-triaryl-6-hydroxy 6-methyl-4-oxocyclohexane-1,3-dicarboxamides.
Abstract: Reaction of N-arylacetoacetamides with aromatic aldehydes in the presence of piperidine in ethanol afforded N,N′,2-triaryl-6-hydroxy-6-methyl-4-oxocyclohexane-1,3-dicarboxamides. The latter reacted with p-toluidine leading to the formation of dehydration products. Reactions of N,N′,2-triaryl-6-hydroxy-6-methyl-4-oxocyclohexane-1,3-dicarboxamides with hydrazine hydrate and cyanoacetic acid hydrazide gave rise to tetrahydroindazoles. Some of the obtained compounds showed antimicrobial activity.
TL;DR: In this article, the synthesis and characterization of four CT complexes of Ty with picric acid (PA), chloranilic acid (CLA), quinol (QL), and 1,3-dinitrobenzene (DNB) was reported.
Abstract: In this paper, we report the synthesis and characterization of four CT complexes of Ty with picric acid (PA), chloranilic acid (CLA), quinol (QL), and 1,3-dinitrobenzene (DNB), and present their thermal decomposition behavior. These complexes were structurally characterized to interpret the behavior of interactions using elemental analysis; IR and 1H NMR spectroscopy. Finally, the thermal behavior of the obtained complexes and the kinetic thermodynamic parameters (E*, A, ΔS*, ΔH*, and ΔG*) were also investigated using Coats-Redfern and Horowitz-Metzger equations.
TL;DR: In this article, the synthesis, physicochemical properties, computational, and antimicrobial activity of the products of chelation of moxifloxacin hydrochloride (mox-HCl) antibiotic drug and metal ions including Ca(II), Mg, Zn, and Fe(III).
Abstract: Metal complexes of antibiotic molecules can be used as antimicrobial mimetic drug models. The current study is devoted to the synthesis, physicochemical properties, computational, and antimicrobial activity of the products of chelation of moxifloxacin hydrochloride (mox-HCl) antibiotic drug and metal ions including Ca(II), Mg(II), Zn(II), and Fe(III). Structures of the complexes were elucidated on the basis of elemental analyses, electronic, IR, Raman, and 1H NMR spectra. The data revealed that chelation of moxifloxacin could follow mono and bidentate pathways. Ca(II), Zn(II) and Fe(III) ions coordinated via N atoms of the piperidyl ring but Mg(II) coordinated via oxygen atoms of the carbonyl (quinolone) and carboxylic groups. According to molar conductance data the complexes had non-electrolyte nature. Formulas of the complexes can be presented as [Mg(mox-HCl)2(Cl)2]·2H2O (1), [Ca(mox-HCl)2(Cl)2]·2H2O (2), [Zn(mox-HCl)2(NO3)2] (3), and [Fe(mox-HCl)3(Cl)3] (4). All synthesized mox-HCl complexes demonstrated some antibacterial but no antifungal activities.
TL;DR: In this article, aryl(hetaryl)-substituted gem-cyanonitroethenes preparation is summarized, and products structure elucidation by means of 1H, 13C NMR, IR, and UV spectroscopy methods is discussed.
Abstract: Methods of aryl(hetaryl)-substituted gem-cyanonitroethenes preparation are summarized, and the products structure elucidation by means of 1H, 13C NMR, IR, and UV spectroscopy methods is discussed. E-Configuration of the compounds obtained has been proved. Reaction of the studied gem-cyanonitroethenes with 2,3-dimethyl-1,3-butadiene affords the diene synthesis adducts–6-aryl(hetaryl)-3,4-dimethyl-1-nitro-1-cyano- 3-cyclohexenes.
TL;DR: In this article, the magnetic properties of cubic and tetragonal modifications of Bi3Nb1-xMnxO7-δ solid solutions have been examined and the magnetic susceptibility studies have revealed that paramagnetic manganese atoms exist as Mn(III) and Mn(IV) monomers as well as exchange-bound dimers.
Abstract: Magnetic behavior of Bi3Nb1–xMnxO7–δ solid solutions of cubic and tetragonal modifications has been examined in comparison. The magnetic susceptibility studies have revealed that paramagnetic manganese atoms in the solid solutions of cubic and tetragonal modification exist as Mn(III) and Mn(IV) monomers as well as exchange-bound dimers: Mn(III)OMn(III), Mn(IV)OMn(IV), and Mn(III)OMn(IV). The exchange parameters and the distribution of monomers and dimers in the solid solutions have been determined as function of the paramagnetic atoms fraction.
TL;DR: In this paper, a simple ligand-free cyclization of propargylic alcohols with enaminones has been developed by using FeBr3 as catalyst, which provides an easy and convenient method to synthesize polysubstituted 1,2-dihydropyridine derivatives.
Abstract: A simple ligand-free cyclization of propargylic alcohols with enaminones has been developed by using FeBr3 as catalyst. This reaction provides an easy and convenient method to synthesize polysubstituted 1,2-dihydropyridine derivatives.
TL;DR: In this article, a silver-containing nanocomposites based on sulfated arabinogalactan have been prepared under mild conditions and shown antimicrobial activity against a wide range of bacteria and fungi.
Abstract: Silver-containing nanocomposites based on sulfated arabinogalactan have been prepared under mild conditions. The products contain 2–12 nm silver nanoparticles stabilized by the polymer. The composites are readily water-soluble and reveal antimicrobial activity against a wide range of bacteria and fungi.
TL;DR: In this paper, a composite of heteropolysaccharide arabinogalactan and elemental selenium (0.54% of Se) has been used for treatment of bone injury.
Abstract: Nanocomposite of heteropolysaccharide arabinogalactan and elemental selenium (0.54% of Se) has been prepared and studied by means of transmission electron microscopy, UV spectroscopy, and X-ray diffraction analysis. Possibility of the composite application for treatment of bone injury has been estimated.
TL;DR: A convenient and efficient synthetic protocol of ionic liquid, 1-n-butyl-3-methylimidazolium tetrachloroferrate, [bmim]Cl·FeCl3 mediated synthesis of novel indolin-2-one annulated spirochromanone conjugates was described, and the synthesized compounds were evaluated for their antioxidant activity.
Abstract: A convenient and efficient synthetic protocol of ionic liquid, 1-n-butyl-3-methylimidazolium tetrachloroferrate, [bmim]Cl·FeCl3 mediated synthesis of novel indolin-2-one annulated spirochromanone conjugates was described. These spirochromanone conjugates were efficiently synthesized by Kabbe condensation of substituted 3-[2-(5-acetyl-2,4-dihydroxyhenyl)-2-oxoethylidene]indolin-2-ones with various cycloalkanones catalyzed by pyrrolidine in ionic liquid [bmim]Cl·FeCl3 under microwave irradiation. This approach offers the advantages of short reaction time, mild reaction conditions, high yields, convenient operation, and reuse of ionic liquid. The synthesized compounds were evaluated for their antioxidant activity. Among the compounds synthesized, IVb and IVd exhibited the highest antioxidant activity. The IC50 values for compounds IVb and IVd were found to be 1.25 and 1.74 μM, respectively, comparable to that of ascorbic acid (IC50 8.64 μM), a standard antioxidant agent.
TL;DR: In this article, X-ray diffraction analysis was used to determine the structure of the dimer Eu2(dpm)6 and mononuclear complexes Ln(dmpz)(dpm).
Abstract: Mixed-ligand complexes of Eu(III) and Tb(III) dipivaloylmethanates with N-heterocyclic ligands (3,5-dimethylpyrazole, imidazole, 4-aminopyridine, 2,2′-bipyridine, and 1,10-phenanthroline) were synthesized. X-ray diffraction analysis was used to determine the structure of the dimer Eu2(dpm)6 and mononuclear complexes Ln(dmpz)(dpm)3 (Ln = Eu, Tb) and Tb(apy)(dpm)3. Photoluminescence of the complexes and their films obtained by chemical vapor deposition was studied.
TL;DR: In this article, the molar mass parameters of polysaccharides with noble metal nanoparticles were determined by means of size-exclusion chromatography (SEC), and the composites were self-assembled via specific interaction of the biopolymers with the surface of the metal particles.
Abstract: Molar mass parameters of galactose-containing polysaccharides constituting composites with noble metal nanoparticles have been determined by means of Size-exclusion chromatography (SEC). The composites are self-assembled via specific interaction of the biopolymers with the surface of the metal nanoparticles. The metal content significantly influences the molar mass parameters of the stabilizing polysaccharides. The change of the polymer of polydispersity is due to their redox interaction with the metal ions as well as due to the alkaline-induced degradation. Increasing the nanoparticles number results in the enhanced macromolecules aggregation.
TL;DR: In this paper, an improved synthetic route for obtaining mixed lanthanide concentrate from digested phosphogypsum solutions with a number of well-known organophosphorus compounds, such as tributyl phosphate, trioctylphosphine oxide, and bis(2-ethylhexyl)-phosphoric acid, was developed.
Abstract: Extraction of rare earth elements from digested phosphogypsum solutions with a number of well-known organophosphorus compounds, tributyl phosphate, trioctylphosphine oxide, and bis(2-ethylhexyl)-phosphoric acid, as well as with phosphoryl ketone Ph2P(O)CHMeCH2C(O)Et, was studied. It was found that this phosphoryl ketone is the most effective reagent for obtaining the mixed lanthanide concentrate. An improved synthetic route to this compound was developed.
TL;DR: In this article, the authors studied the presence and coexisting forms of titanium in surface waters and found that the ratio of dissolved to suspended titanium in water bodies depends on the content of suspended matter and its nature.
Abstract: Results obtained in studying the content and coexisting forms of titanium in surface waters are given. It was established that the titanium concentration lies within 0.0–1180 μg/L in the world’s surface water and within 0.0–573 μg/L in the studied water bodies of Ukraine. The concentration of dissolved and suspended titanium in the water bodies studied also varies within the wide range, 0.0–86.0 and 0.0–534.6 μg/L, respectively. The concentration of its dissolved form in world’s surface water is 0.0–68.7 μg/L. The ratio of dissolved to suspended titanium in water bodies depends on the content of suspended matter and its nature. In river waters, the suspended titanium mostly dominates over the dissolved form. We found that in rivers with the high concentration of suspended matter (6.0–140.6 mg/L), mostly of mineral nature, a fraction of the suspended titanium reaches 62.3–88.6% on the average. A strong correlation between the mass of suspended matter and the concentration of suspended titanium in these surface waters shows that the nature of suspended matter affects the concentration of suspended titanium. The correlation coefficient is between 0.81–0.99 at a significance level of 0.01. The titanium content in the suspended matter and bottom sediments of world’s water bodies makes 0.2–19.8 and 0.1–24.6 mg/g of dry weight of the suspended matter, respectively. In the surface waters studied, its content ranges within 0.0–16.5 mg/g of dry weight of the suspended matter. Taking into account the average values, the titanium content in the suspended matter of the studied rivers, water reservoirs, lakes, and ponds is (mg/g in terms of dry mass): 1.0–7.5, 1.0–4.9, 1.3–3.9, and 1.2–1.3, respectively. The percentage of the adsorbed titanium in the suspended matter of the Kilia Danube delta, Kanev Reservoir, and the Lybid’ River is 91.6–97.3, 67.6–74.4, and 57.1–99.4%, respectively. The acidic (anionic), basic (cationic), and neutral fractions of the dissolved organic substances in the surface waters contained 15.7–89.4, 0.0–33.8, and 0.0–80.7% of dissolved titanium (Tidiss) (i.e., 44.4, 13.2, and 42.4% of Tidiss on the average). The presence of dissolved titanium in the anionic fraction shows that titanium forms complexes with humic substances or exists in the form of TiO2 colloidal particles (nanoparticles) coated with humic substances. In the neutral fraction, a hydrated titanium oxide TiO(OH)2 may exist as a form of its migration in natural surface waters.
TL;DR: A series of linear and macrocyclic tetrapeptide derivatives based on Nα-dinicotinoyl-bis[L-leucyl-L-phenylalaninyl] acid hydrazide as starting material is synthesized as discussed by the authors.
Abstract: A series of several linear and macrocyclic tetrapeptide derivatives based on Nα-dinicotinoyl-bis[L-leucyl-L-phenylalaninyl] acid hydrazide as starting material is synthesized. Treatment of acid hydrazide with cyclic alkanones gave the corresponding tetrapeptide cycloalkanone derivatives. Condensation of hydrazide with substituted acetophenone or acetylpyridine derivatives gave the corresponding Schiff base derivatives. Cyclization of acid hydrazide with 2,6-diacetylpyridine afforded the corresponding bicyclopyridine derivative. Reaction of acid hydrazide with acids anhydrides gave the corresponding bisimide carboxamide derivatives.