Journal of Organic and Pharmaceutical Chemistry

Prospects for the search of antiviral agents among 4-thiazolidinone derivatives, as well as the optimal directions of the main core structure optimization – namely C5 and N3, have been described. As the result of the screening performed (within the Antimicrobial Acquisition and Coordinating Facility programme), the values of the antiviral activity of the target 5-substituted-4-thiazolidinones with the carboxylic group (or its derivatives) in the N3 residue on relation to a wide range of the viral panels have been determined. The active compounds, which can be regarded as promising structures in the anti-flu agent design, have been identified, as well as 3-{5-[2-chloro-3-(4-nitrophenyl)-allylidene]-4-oxo-2-thioxothiazolidine-3-yl}-propionic (1) and –succinic acids (3) have been identified has hit-compounds with a marked anti-VZV activity (SI values – 27 and 38, respectively).

At the present stage of development of organic chemistry there are a lot of basic synthetic approaches to synthesis of 1,3,4-oksadiazole derivatives with a wide spectrum of biological activity. The heterocyclic systems which contain 1,3,4-oksadiazole nucleus have a rich synthetic history and they are characterized by a wide range of methods of synthesis. In the review for the first time have been systematized and summarized literature sources for the chemistry of heteryl derivatives of 2,5-disubstituted 1,3,4-oxadiazole as important synthetic substrates and precursors for the design of biologically active substances. There have been considered the main approaches to synthesis of this series of compounds, which consist in the intramolecular dehydration of 1,2-diacylhydrazine, in the interaction of hydrazides of heterylcarbonic acids with carbonyl dichloride, orthoethers, carbon (IV) sulfide and in the formation of an oxadiazole nucleus based on functional acylthiosemicarbazide and hydrazone. A significant emphasis is concentrated on the cyclodehydration reaction of N,N’-diacylhydrazide using dehydrating agents, which are a powerful tool for constructing their synthetically and biologically attractive derivatives.
There have been analyzed in detail the methods for the preparation of acridone derivatives which contain the 1,3,4-oxadiazole fragment, have been delineated their preparative boundaries and has been revealed the biological potential. It is important to note that the processes of heteryl functionalization are new in the chemistry of 1,3,4-oxadiazole and they allow us to obtain new bioperspective hybrid structures. Analysis of literature data shows that the derivatives of 2,5-disubstituted 1,3,4-oxadiazole are considered as promising substances with antibacterial, fungicidal, anti-inflammatory, hypoglycemic, antimalarial activity. The search for biologically active substances in this series of compounds is expedient and has practical and theoretical significance.

Nowadays the problem of the antimicrobial resistance promotes the search of new chemical core-structures with the antimicrobial properties.
Aim. To study the interaction of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with active methylene nitriles and aliphatic aldehydes and assess the antimicrobial activity of the compounds obtained.
Results and discussion. 1,2-Benzoxathiin-4(3H)-one 2,2-dioxide as a structural analog of 1,3-dicarbonyl compounds was used in the three-component interaction with aliphatic aldehydes and active methylene nitriles. In the case of malononitrile the target compounds were formed. When using ethyl cyanoacetate the only isolated product was triethylammonium salt that could be also obtained by the two-component reaction of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with aliphatic aldehydes. The study of the antimicrobial properties showed the higher activity of the compounds studied than in the reference drugs, especially against gram-positive strains.
Experimental part. The series of 2-amino-4-alkyl-4,6-dihydropyrano[3,2-c][2,1]benzoxathiin-3-carbonitrile 5,5-dioxides and triethylammonium 3-[1-(4-hydroxy-2,2-dioxido-1,2-benzoxathiin-3-yl)alkyl]-1,2-benzoxathiin-4-olate 2,2-dioxides was synthesized. The antimicrobial activity of the compounds obtained was determined by the agar “well” diffusion method.
Conclusions. It has been shown that 1,2-benzoxathiin-4(3H)-one 2,2-dioxide as a structural analog of 1H-2,1-benzothiazin-4-one 2,2-dioxide can be used in similar three- and two-component reactions, but its reactivity is less due to the replacement of the 1-N-R-group with an O-atom. The novel compounds obtained exceeded the antimicrobial activity of the reference drugs, and were more active against gram-positive bacteria in contrast to isosteric derivatives of 1H-2,1-benzothiazin-4-one 2,2-dioxide that were active against gram-negative strains and fungi.

It has been previously shown that phosphonic acids covalently attached to the macrocyclic platform of calix[4]arenes are capable of inhibiting alkaline phosphatases. In this paper the effects of the upper-rim functionalized calix[4]arenes on the activity of nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) have been examined.
Aim. To assess the inhibitory potential of calix[4]arene, thiacalix[4]arene and sulfonylcalix[4]arene derivatives against NPP1.
Results and discussion. It has been found that calix[4]arene, thiacalix[4]arene, and sulfonylcalix[4]arene tetrakismethylphosphonic acids inhibit NPP1 with the IC50 values in the micromolar range. The derivatives of sulfonylcalix[4]arene demonstrated the selectivity of inhibition of NPP1 over alkaline phosphatases. In addition, sulfonylcalix[4]arene tetrakismethylphosphonic acid was able to inhibit the nucleotide pyrophosphatase/phosphodiesterase activity of the human serum. The possible mechanism of the inhibition has been discussed.
Experimental part. The activity of NPP1 was monitored by spectrophotometry measuring the rate of hydrolysis of bis-p-nitrophenyl phosphate. The phosphodiesterase activity of the human serum was assessed in the presence of p-nitrophenyl ester of thymidine-5-monophosphate as a substrate. The homology model of the human NPP1 was generated based on the crystal structure of the murine enzyme. The molecular docking was performed using AutoDock 4.2.
Conclusions. The results obtained have shown the ability of sulfonylcalix[4]arene derivatives to inhibit the activity of NPP1 in vitro, including the nucleotide pyrophosphatase/phosphodiesterase activity in the human blood serum.

The search for new groups of anti-inflammatory and analgesic drugs is a topical issue of the current medicinal chemistry. It is caused by numerous diseases that are accompanied by pain and inflammation, as well as by imperfection of the existing drugs aimed to provide treatment of these pathological conditions. Derivatives of 1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide are promising chemicals to search and develop drugs with the pharmacological properties required. This heterocyclic system is structurally close to 2H-1,2-benzothiazin-4-one 1,1-dioxide, which is the core of the famous non-steroidal anti-inflammatory drugs related to the “oxicam” group. Moreover, derivatives of 1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide are also considered to be promising structures for searching effective antimicrobial substances among them. The present article is devoted to the synthesis of new derivatives of 1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide, namely ethyl 2-amino-4-alkyl-4,6-dihydropyrano[3,2-c][2,1]benzothiazin-3-carboxylate 5,5-dioxides and triethylammonium 3-[(4-hydroxy-1-ethyl-2,2-dioxido-1H-2,1-benzothiazin-3-yl)alkyl]-1-ethyl-1H-2,1-benzothiazin-5-olat 2,2-dioxides. Condensed 2-amino-4-alkyl-4H-pyran-3-carboxylates were synthesized via the three-component one-pot interaction of 1-ethyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide with ethyl cyanoacetate and aliphatic aldehydes. The abovementioned triethylammonium salts were obtained by the two component interaction of 1-ethyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide with aliphatic aldehydes in the presence of the equimolar amount of triethylamine. The study of the anti-inflammatory and analgesic activity has demonstrated high prospects of new effective drugs when searching among two classes of the compounds synthesized. The screening of the antimicrobial activity has shown that the compounds synthesized are the most active against the fungal strain of C. albicans.

Species of Iris genus (Iridaceae) have a long history of traditional medicinal use in different countries as alternative aperient, tonic, cathartic, diuretic, gall bladder diseases, liver complaints, dropsy, purification of blood, venereal infections, fever, bilious infections and for a variety of heart diseases. The rhizomes of Iris are the rich source of the secondary metabolites, in which flavonoids predominate. The clinical studies of substances from irises gave positive results in the treatment of cancer, bacterial and viral infections. Continuing the search of new biologically active compounds from the plants of Iridaceae family for the first time three isoflavones that are new for this species – irigenin, iristectorigenin B and its glucoside iristectorin B have been isolated from the ethanolic extract of the rhizomes of Iris hungarica Waldst. et Kit., which is widespread in Ukraine. The structure of the compounds is described as 5,7,3’-trihydroxy-6,4’,5’-trimethoxyisoflavone, 5,7,4’-trihydroxy-6,3’-dimethoxyisoflavone and iristectorigenin B-7-O-β-D-glucoside, respectively. The compounds were obtained from the ethyl acetate fraction of the iris rhizomes by column chromatography on silica gel with sequential elution of the chloroform – ethanol solvent with different concentrations. The structure of the compounds has been determined by chemical and spectral methods and in comparison with the literature data.

Multicomponent domino reactions are an effective modern approach in the synthesis of different types of organic compounds, including biologically active pyrans.
Aim. To study the three-component interaction of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with different hetarenecarbaldehydes and active methylene nitriles in order to synthesize new 2-amino-4H-pyran derivatives, as well as the antimicrobial activity of the compounds obtained.
Results and discussion. 2-Amino-4-heteryl-4,6-dihydropyrano[3,2-c][2,1]benzoxathiin-3-carbonitrile 5,5-dioxides were obtained by stepwise and multicomponent reactions of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with hetarenecarbaldehydes and malononitrile. For the same interaction with ethyl cyanoacetate the reaction selectivity decreased and not only target ethyl 2-amino-4H-pyran-3-carboxylates were obtained, but also triethylammonium salts of bis(1,2-benzoxathiin-2,2-dioxo-4-ol-3-yl)(heteryl)methane. The latter were also purposefully synthesized by the two-component reaction of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with hetarenecarbaldehydes in the presence of triethylamine. The compounds obtained revealed a higher antimicrobial activity against gram-positive bacteria and fungi compared to the reference drugs.
Experimental part. 3-Amino-4-heteryl-4,6-dihydropyrano[3,2-c][2,1]benzoxathiin-3-carbonitrile 5,5-dioxides and triethylammonium 3-[1-(4-hydroxy-2,2-dioxido-1,2-benzoxathiin-3-yl)heteryl]-1,2-benzoxathiin-4-olate 2,2-dioxides were synthesized. The antimicrobial activity of the compounds synthesized was studied by the agar diffusion method.
Conclusions. It has been proven that the multicomponent format for the three-component interaction of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with hetarenecarbaldehydes and active methylene nitriles is more favorable and convenient than the stepwise approach to obtain new derivatives of 2-amino-4H-pyrans. Triethylammonium 3-[(4-hydroxy-2,2-dioxido-2,1-benzoxathiin-3-yl)heteryl]-2,1-benzoxathiin-5-olate 2,2-dioxides have been also synthesized. The antimicrobial properties of the compounds obtained are higher than in the reference drugs, especially against gram-positive bacteria and fungi.

Much attention is currently paid to the study of the antioxidant properties of various objects – individual antioxidants, dietary supplements, medicines, liquid plant extracts. Antioxidant medicines are widely used as the main or additional correction agents in the treatment of a number of diseases. Therefore, the study and development of procedures for determining the antioxidant activity is a prospective task for today.

Aim. To determine the contribution of different concentrations of ethanol to the level of the antioxidant activity (AOA) of ascorbic acid solutions by the potentiometric method.

Results and discussion. The different ethanol content in the solution had the following percent of the contribution to the value of AOA of ascorbic acid solutions – 1.85, 3.56, 4.89, 6.76, 7.63 % for 20, 40, 60, 80, 96 % ethanol, respectively. The linearity of the procedure was proven in the range from 0.039 to 0.31 mmol/L.

Experimental part. The object of the study was solutions of ascorbic acid prepared using ethanol of different concentrations – 20, 40, 60, 80, 96 %. Potentiometric measurements were conducted by a Hanna 2550 pH meter (Germany) with an EZDO 5010 combined platinum electrode. Weighing was carried out using an АN100 digital analytical balance (AXIS, Ukraine) with d = 0.0001 g. Ascorbic acid was purchased from Sigma Aldrich (≥ 99.0 %), K₃[Fe(CN)₆], K₄[Fe(CN)₆], NaHPO₄, KH₂PO₄ were of analytical grade.

Conclusions. It has been found that ethyl alcohol affects the change of the potential in the electrochemical cell and the level of AOA of ascorbic acid solutions. The percentage of the contribution of different concentrations of ethyl alcohol to the AOA value ranges from 1.85 to 7.63 %. The approach and the formula for calculation that take into account the effect of ethyl alcohol on the final AOA result of the test sample of ascorbic acid in a water-alcohol solutions have been proposed. The results of this study can be used in the pharmaceutical and food industries to determine, assess and control the AOA level of dietary supplements, liquid extracts, tinctures, medicines, and alcoholic beverages.

Two approaches for synthesis of a great variety of 3-N-substituted 1H-thieno[3,2-d]pyrimidine-2,4-diones have been investigated. The first one is based on the interaction of methyl 3-aminothiophene-2-carboxylate with isocyanates, which is a good way for preparation of 3-N-aryl-1H-thieno[3,2-d]pyrimidine-2,4-diones. The key step of the other one, which allows introduction of different alkyl substituents in position 3, is oxidation of 4-oxo-2-thioxo-2,3- dihydrothieno[3,2-d]pyrimidines prepared by interaction of 3-isothiocyanatothiophene-2-carboxylate and the primary aliphatic amines with hydrogen peroxide. Alkylation of the intermediates obtained in both ways resulted in 1-N-alkyl-3-N-substituted 1Н-thieno[3,2-d]pyrimidine-2,4-diones. 1H NMR spectra of the target molecules contain the signals of thiophene cycle protons H-6 (δ 8.02-8.18 ppm) and H-7 (δ 7.06-7.15 ppm) together with the signal of CH2 groups in position 1 of the heterocyclic system in the range of δ 4.70-5.20 ppm. The antimicrobial activity of the compounds synthesized has been investigated by the agar well diffusion method. It has been determined that the compound with phenyl substituents in position 3 and o-methylbenzyl substituent in position 1 is the most active antimicrobial agent. The 1-N-alkyl derivatives of 2,4-dioxo-1,4-dihydro-2H-thieno[3,2-d]pyrimidine-3-yl)propanoic acid benzyl amide appeared to be active against the strains of Staphylococcus aureus and Bacillus subtilis.

Aim. To develop an alternative method for the quantitative determination of the benzalkonium chloride content as an active pharmaceutical ingredient in the disinfectant solution “CUTASEPT® F”.
Materials and methods. The method is based on the ability of benzalkonium chloride to inhibit the enzymatic hydrolysis of acetylcholine by acetylcholinesterase. The reaction rate is assessed by the non-hydrolyzed acetylcholine residue, which is determined by the amount of peracetic acid produced during the interaction with the excess of the hydrogen peroxide solution. The indicator reaction is the interaction of p-phenetidine with peracetic acid that leads to the formation of 4,4’-azoxyphenetole with λ_max = 358 nm (log₁₀ ε = 4.2).
Results and discussion. As a result of the research conducted the linear dependence of the degree of inhibition of the enzymatic hydrolysis of acetylcholine (U, %) on the concentration of benzalkonium chloride was determined in the concentration range of (0.5 – 7.0) × 10^–6 mol L^-1 with the correlation coefficient of 0.999. The limit of quantitation was 1.9 × 10^–6 mol L^-1.
Conclusions. As a result of the research conducted the kinetic enzymatic method for the quantitative determination of benzalkonium chloride has been developed by its inhibitory effect in the biochemical reaction of acetylcholine hydrolysis. This method is fast, cheap and easy to perform, does not require expensive equipment, and available for use in the field.

Aim. To study the qualitative composition, the quantitative content of catechins in green tea leaves and compare the data obtained with those evaluated by spectrophotometry.
Materials and methods. Green tea leaves used for the analysis were collected in Anhui Province, China. The extract for the HPLC analysis was obtained by the maceration method with 60 % ethanol twice in the raw material/extractant ratio of 1 : 20. In the case of the spectrophotometric analysis, green tea leaves were extracted with 70 % ethanol twice by the maceration method in the raw material/extractant ratio of 1 : 20. The analysis of the extract from green tea leaves was performed by high performance liquid chromatography using a Prominence LC-20 Shimadzu chromatographic system (Japan) with a SPD-20AV spectrophotometric detector, an Agilent Technologies Microsorb-MV-150 column (reversed phase, C18 modified silica gel, length – 150 mm, diameter – 4.6 mm, particles size – 5 μm). Substances in the extract were identified by comparing the retention time and the spectral characteristics of the test substances with the same characteristics of the reference standards. Spectrophotometric measurements were carried out using a UV-1000 single beam spectrophotometer (China) with the pair of S90-309Q quartz square cells.
Results and discussion. Using high performance liquid chromatography 5 catechins were identified.
Among them epigallocatechin-3-O-gallate (10.85 %) predominated, while catechin (0.61 %) had the lowest concentration. The total amount of catechins in green tea leaves was 30.56 and 24.79 % by HPLC and spectrophotometry, respectively. The F- and t-tests showed that there was no significant difference between the results of HPLC and spectrophotometry.
Conclusions. The qualitative composition and the quantitative content of catechins have been determined in the extract from green tea leaves by high performance liquid chromatography and spectrophotometry. Both HPLC and spectrophotometric methods can be used to determine the total catechin content in green tea leaves. The high content of catechins makes the extract promising for further study and creation of new herbal medicinal products and dietary supplements. The results obtained will be used for standardization of green tea leaves and for future pharmacological research of its extract.

The review systematizes the literary data on the methods of the synthesis of 4-phosphorylated 1,3-azoles (oxazoles, thiazoles, selenazoles, imidazoles), as well as their chemical and biological properties. For the synthesis of 4-phosphorylated imidazole derivatives metallic derivatives of imidazole and phosphorus halides, electronically enriched imidazoles and phosphorus halides in pyridine in the presence of triethylamine or a cross-coupling of halogenimidazoles and dialkyl phosphites in the presence of a palladium catalyst are generally used. For the synthesis of 4-phosphorylated 1,3-azoles the acyclic phosphorus-containing reagents have been widely used, in particular 1-phosphorylated derivatives of 2-chloro- and 2,2-dichloroethenylamides, aminomethylphosphonates and their triphenylphosphonium analogs, β-ketopphosphonates, phosphorylated α-halogenocarbonyl compounds. The chemical properties of phosphorylated azoles are represented by phosphorus residue modification reactions, modification of other substituents and the azole ring, as well as reactions involving the disclosure of the azole ring. The latter are the most interesting since they provide an opportunity to conduct recyclization reactions, as well as synthesize an important class of organic compounds – phosphorylated peptidomimetics. Due to the systematic study of derivatives of 1,3-azoles over the last 30 years it has been shown that at least one fragment of the 1,3-azole ring is a part of a wide range of simple and complex natural molecules and synthetic drugs. Synthetic 4-phosphorylated derivatives of 1,3-azoles are characterized by insectoacaricidal, anti-blastic, sugar-lowering, anti-exudative, antihypertensive, neurodegenerative and other types of activity.

Aim. To develop the preparative methods for obtaining new series of biologically active substances by the three-component interaction between isatin, α-amino acids and N,N’-di(3-carboxypropenoyl)-1,2-ethylenediamine and determine the structure of the compounds obtained.
Results and discussion. Using the three-component cascade transformation of isatin with α-amino acids and N,N’-di(3-carboxypropenoyl)-1,2-ethylenediamine a series of new derivatives of ethylene-N,N’-bis(spiroindole- 3,3’-pyrrolo[3,4-c]pyrrole-2a’,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-trione) was synthesized. It was found that as a result of N,N’-di(3-carboxypropenoyl)-1,2-ethylenediamine cyclization in the course of the reaction the derivatives of N,N’-ethan-1,2-diyl-bis-spiro-2-oxidol[3,2’]-3’H,4’H,5’H-pyrrolo-4’-carboxy-3’-carboxamide were not formed. Instead of the expected hypothetical structures the derivatives of ethylene-N,N’-bis(spiroindole-3,3’-pyrrolo[3,4- c]pyrrole-2a’,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-trione) were selected. The structure of the compounds synthesized was reliably proven by the instrumental methods (1H NMR, IR-spectroscopy), as well as counter synthesis.
Experimental part. The synthesis of compounds was performed using the three-component condensation in the alcoholic-aqueous medium and instrumental methods for determining the structure of organic compounds.
Conclusions. The reaction of the three-component interaction between isatin, α-amino acids and N,N’- di(3-carboxypropenoyl)-1,2-ethylenediamine has been studied. It has been proven that the preparatory method for the three-component cascade transformation of isatin with α-amino acids and ethylenebismaleinimide is an effective method for the synthesis of ethylene-N,N’-bis(spiroindole-3,3’-pyrrolo[3,4-c]pyrrole-2a’,5a’-dihydro-2,2’,6’(1H,1’H,5’H)-triones). The structure of the compounds obtained has been proven.

Secnidazole is one of antiprotozoal medicines from the group of 5-nitroimidazoles, the method of HPLC with different types of detection is widely used for secnidazole determination.
Aim. To develop the HPLC/UV-procedure of secnidazole quantification with application of the system of a “MiLiChrome® A-02” HPLC-analyzer and carry out the step-by-step validation of the procedure developed. Results and discussion. The specificity of the chromatographic conditions proposed was confirmed in relation to other medicines of the group of 5-nitroimidazoles (metronidazole, tinidazole, ornidazole and nimorazole). The retention time for secnidazole was 8.16 min. 0.01 M solution of hydrochloric acid was proposed for preparation of the reference and model solutions in developing the HPLC/UV-procedure of secnidazole quantification. To prove the possibility of application of the procedure proposed in further analysis its validation was carried out in the variants of the method of the calibration curve and the method of standard. Such validation parameters as in-process stability, linearity/calibration model, accuracy and precision (repeatability) were estimated using model solutions.      Experimental part. The HPLC/UV analyses were performed using a MiLiChrome® A-02 high pressure liquid chromatograph (EcoNova, Russia). Eluent A (0.2 M LiClO4 – 0.005 M HClO4) and Eluent B (acetonitrile) were used as the mobile phase components. The HPLC microcolumn with the size of Ø2 × 75 mm and the ProntoSIL 120-5-C18 AQ reversed phase, 5 μm (BISCHOFF Analysentechnik und -geräte GmbH, Germany) was used as an analytical column. The analysis was performed at 40 °С and the flow rate of 100 μl/min. The mobile phase was run in the gradient elution mode, namely from 5 % to 100 % of Eluent B for 40 min, then 100 % of Eluent B for 3 min. Detection was performed at 277 nm.                                                                      Conclusions. A new procedure of the secnidazole quantitative determination by the method of HPLC/UV has been developed. Its validation has been carried out, and acceptability for its application has been shown.

Aim. To determine the direction of the interaction of isatins with 5-amino-pyrazoles and 2,2-dimethyl-1,3-dioxane-4,6-dione under different conditions.

Results and discussion. The domino-reactions of isatins, 5-aminopyrazoles and 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum’s acid) in the alcoholic medium are completed by formation of a mixture of pyrazolo[3,4-b]pyridine-4-spiroindolinones and 3-(5-aminopyrazol-3-yl)-3-hydroxy-2-oxindolines with the predominant content of spiro compounds. 3-(5-Aminopyrazol-4-yl)-3-hydroxy-2-oxindolines may turn into pyrazolo[3,4-b]pyridine-4-spiroindolinones very slowly only as a result of retrograde fragmentation to isatin and aminopyrazole in the presence of Meldrum’s acid.

Experimental part. The mixtures of pyrazolo[3,4-b]pyridine-4-spiroindolinones and 3-(5-aminopyrazol-3-yl)-3-hydroxy-2-oxindolines separated by crystallization were obtained by boiling in methanol of the equimolar quantity of isatins, 5-aminopyrazoles and Meldrum’s acids. The yield for spiro compounds is 26-82 %, and for 3-(5-aminopyrazole-3-yl)-3-hydroxy-2-oxindolines it is 5-23 %. The transformation of the latter into the spiro compound in the presence of Meldrum’s acid occurs with prolonged boiling in the alcoholic medium and is accompanied with extremely low yields. The structure of all compounds synthesized has been proven by ¹H NMR, mass spectra and elemental analysis.

Conclusions. It has been found that in the three-component reactions of isatins, 5-aminopyrazoles and 2,2-dimethyl-1,3-dioxane-4,6-dione there are two competing directions of the interaction of isatin with nucleophiles. One of them is the nucleophilic addition of the C⁴ reaction center of aminopyrazole to the carbonyl group of isatin, which results in 3-(5-aminopyrazol-4-yl)-3-hydroxy-2-oxidolines. Another one is the Knoevenagel condensation of isatin with dioxane-4,6-dione – a domino process that starts formation of the predominant reaction products – pyrazolo[3,4-b]pyridine-4-spiroindolinones.

In the pharmaceutical practice directly related to the search of biological active substances and their introduction into medicine or veterinary it is generally recognized that a successful choice of the research object is a prerequisite for a positive final outcome to create original effective and low-toxic drugs. At present, derivatives of 1,2,4-triazoles containing pyridine deserve special attention. That is why the synthesis and study of physicochemical properties of new compounds, which contain 1,2,4-triazole and pyridine rings, are important tasks of modern synthetic and pharmaceutical chemistry.

Aim. To study the reactions associated with formation and transformation of 6-((5-phenethyl-4-R-1,2,4-triazole-3-ylthio)pyridine-3-yl)-(alkyl-, heteryl)methanimines and their recovery, study physicochemical properties of new compounds synthesized.

Materials and methods. 6-((5-phenethyl-4-R-1,2,4-triazole-3-ylthio)pyridine-3-yl)-(alkyl-, heter-yl)methanimines were obtained by the mixture from 6-(5-phenethyl-4-R-1,2,4-triazole-3-ylthio)pyridine-3-amine and aldehydes. The synthesis was carried out in the acetic acid medium. The mixture was kept at room temperature for 6 h. 6-((5-phenethyl-4-R-1,2,4-triazole-3-ylthio)pyridine-3-yl)-(alkyl-, heteryl)methanimines were reduced in the 1,4-dioxane medium. As a reducing agent sodium borohydride was used.

Results and discussion. As a result of synthetic transformations 17 new compounds have been obtained, the structure of the compounds synthesized has been confirmed by modern complex of physicochemical methods of analysis (IR-spectrophotometry, elemental analysis), and their individuality has been proven on an Agilent 1260 Infinity HPLC high-performance liquid chromatograph equipped with an Agilent 6120 mass spectrometer.

Conclusions. The preparative method for the synthesis of 6-((5-phenethyl-4-R-1,2,4-triazole-3-ylthio)pyridine-3-yl)-(alkyl-, heteryl)methanimines and 6-(5-phenethyl-4-R-1,2,4-triazole-3-ylthio)-N-(alkyl-, heteryl)pyridine-3-amines has been developed.

Fused heterocyclic 1,2,4-triazoles have provided much attention due to variety of their interesting biological properties.

Aim. To develop the method for the synthesis of novel 2-[(1,2,4-oxadiazol-5-yl)-[1,2,4]triazolo[4,3-a]pyridine-3-yl]acetamides and conduct the biological assessment of the compounds synthesized.

Results and discussion. A diverse set of acetamides newly synthesized consists of 32 analogs bearing an 1,2,4-oxadiazole cycle in positions 6, 7 and 8. A convenient scheme of the synthesis starts from commercially available 2-chloropyridine-3-, 2-chloropyridine-4-, 2-chloropyridine-5-carboxylic acids with amidoximes to form the corresponding 2-chloro-[3-R₁-1,2,4-oxadiazol-5-yl]pyridines, then follows the reaction of  hydrazinolysis with an excess of hydrazine hydrate. The process continues via the ester formation with the pyridine ring closure, then the amide formations of the end products are obtained by hydrolysis into acetic acid.

Experimental part. A series of new 2-[6-(1,2,4-oxadiazol-5-yl)-, 2-[7-(1,2,4-oxadiazol-5-yl)-, 2-[8-(1,2,4-oxadiazol-5-yl)-[1,2,4]triazolo[4,3-a]pyridine-3-yl]acetamides were obtained in good yields, and their structures were proven by the method of ¹H NMR spectroscopy. The prognosis and study of their pharmacological activity were also conducted.

Conclusions. The synthetic approach of obtaining the representatives of 2-[(1,2,4-oxadiazol-5-yl)-[1,2,4]triazolo[4,3-a]pyridine-3-yl]acetamides previously unknown can be used as an applicable method for the synthesis of diverse functionalized [1,2,4]triazolo[4,3-a]pyridine derivatives.

Aim. To determine the parameters of standardization of a dry extract from large cranberry (Oxycoccus macrocarpus (Ait.)) leaves and a dry extract modified with arginine and develop projects of Drug Quality Control Methods (DQCM) for these substances.
Materials and methods. The study object was dry extracts from large cranberry leaves. Leaves were harvested in October 2021 in the Zhytomyr region (Kostivtsi village, 50.326862437345945, 29.54310845594284). The extracts were obtained with a 50 % solution of ethyl alcohol in the ratio of 1:30 by double maceration. Half of the combined extract was dried to a dry extract (Extract 1), and the other half was modified with arginine in the threefold equimolar amount relative to the total amount of phenolic compounds and evaporated to a dry extract (Extract 2). Standard pharmacopoeial methods were used to determine standardization parameters. The quantitative determination was carried out using the spectrophotometric method by the content of flavonoids calculated with reference to hyperoside and hydroxycinnamic acids calculated with reference to chlorogenic acid on an Evolution 60S spectrophotometer (Thermo Scientific Spectronic, USA).
Results and discussion. The parameters of standardization of dry extracts from large cranberry leaves were determined. The project of DQCM was proposed according to the following indicators: description, solubility, identification using the thin-layer chromatography method (by the content of flavonoids, hydroxycinnic acids and arginine), loss on drying, the residual amount of organic solvents (ethanol), microbiological purity, and the content of heavy metals. The assay was carried out using spectrophotometry by the content of flavonoids and derivatives of hydroxycinnic acids. Three batches of the extracts obtained, which fully corresponded to the projects of DQCM developed, were analyzed.
Conclusions. The parameters of standardization of dry extracts from large cranberry leaves have been determined, and projects of DQCM for the substances obtained have been developed. It is the basis for creating new medicines for the correction of insulin-resistant conditions in Type 2 diabetes mellitus.

Aim. To develop a principally new method, which would allow achieving the necessary accuracy and reproducibility of the analysis results, for determining the activity of the blood cholinesterase; to create safe working conditions when performing the analysis.

Results and discussion. The kinetic method proposed for determining the activity of cholinesterase consists in photometric measurement of the rate of the enzymatic hydrolysis of the acetylcholine substrate (by its residue) in the phosphate buffer using p-phenetidine as an indicator. The rate of the enzymatic hydrolysis of acetylcholine was determined by the tangent of the inclination angle of the linear part of the kinetic curve in the А–t coordinates at a wavelength of 358 nm. The linear dependence of the conditional reaction rate (tgα) on the enzyme concentration was observed in the concentration range of 0.12 – 0.36 mg/mL. Metrological characteristics of the method developed were: RSD = 2.0 % (n = 5; P = 0.95), correctness 0.4 %. These values indicate that the method for determining the activity of blood cholinesterase is sensitive, reliable and reproducible.

Experimental part. The experiments on determining the rate of the enzymatic hydrolysis were repeated three times with a specific concentration of the enzyme. Using the data obtained the kinetic curves were constructed in the А–t coordinates; on their basis the tangents of the angles of inclination in min^-1 were calculated. The calibration graph was constructed using the average values of the tangents of the angles of inclination, which corresponded to a certain concentration of the solution of the working standard sample of the enzyme. The equation of the calibration dependence of tgα-enzyme concentration was calculated by the method of least squares and found to be tgα (min^-1) = –0.17с + 9.13 (r = 0.999).

Conclusions. As a result of the studies conducted, a new method for determining the activity of the cholinesterase enzyme has been developed. The method is characterized by a high sensitivity, reliability and reproducibility and provides safe working conditions when performing the analysis.

Aim. To generalize and systematize information on the properties of modern chemical disinfectants and antiseptic agents (DA and AA).
Results and discussion. The review provides generalized and systematized information on the properties of modern chemical DA and AA – alkylating reagents, aldehydes, amides, amidines, bisguanidines, dyes, halogenated reagents, halogens and their complexes, 2-nitrofuran derivatives. The classification of DA and AA by their chemical structure was carried out. The activity spectra, possible application ways and forms of DA and AA were given. Their toxicity and impact on the environment were described as well.
Conclusions. On the basis of the analysis carried out it was shown that aldehydes, halogen-active compounds and halogen-containing complexes are modern effective DA and AA with a wide spectrum of biocidal action. Amides, amidines and bisguanidines are characterized by a narrow spectrum of activity. Dyes and 2-nitrofuran derivatives are old-fashioned antiseptics.

The uncontrolled simultaneous application of prochlorperazine with typical phenothiazine derivatives antipsychotics and other drugs leads to fatal poisonings.

Aim. To optimize TLC procedures for the screening examinations in combined poisonings with prochlorperazine and other drugs.

Results and discussion. The chromatographic mobility of prochlorperazine, clorpromazine, ibuprofen, trifluoperazine and quetiapine has been studied on two types of plates (HPTLC and TLC). It has been shown that the TLC-systems used (special – for prochlorperazine, general – for screening of phenothiazine derivatives, as well as drug and narcotic substances of the basic nature recommended by the International Association of Forensic Toxicologists) rather effectively separate the substances analyzed in a thin layer of a sorbent, except for trifluoperazine. To detect the adsorption zones of substances, the Lieberman reagent giving different staining, the Dragendorff reagent and irradiation of chromatograms by UV-light (λ = 254 nm) have been proposed. The detection sensitivity is 0.5 – 1.0 μg in the sample. The validation assessment of the methods developed has been carried out by the chromatographic analysis of prochlorperazine model mixtures with each of the substances studied.

Experimental part. The studies were carried out on HPTLC plates (silica gel 60G, particle size – 5 – 7 μm, substrate type – glass, Estonia) with 10 × 10 cm in size and Merck plates (silica gel 60G F₂₅₄, particle size – 10 – 15 μm, substrate type – aluminum foil, Germany) with 10 × 10 cm in size.

Conclusions. The TLC-conditions for screening of prochlorperazine, chlorpromazine, ibuprofen, trifluoperazin and quetiapine have been determined; they can be recommended for drugs detection in real samples of biological objects in the case of combined poisoning.

Received: 17.02.2020
Revised: 15.04.2020
Accepted: 29.05.2020

Aim. To develop the optimal method for the synthesis of new polysubstituted thienylpyrroles and study them as cereal growth stimulants.
Results and discussion. Preparative methods for the synthesis of 4-(5-carboxythiophen-2-yl)-3,5-dimethyl-1H-pyrrole-2-carboxylic acid, 5-(5-carboxythiophen-2-yl)-2,4-dimethyl-1H-pyrrol-3-carboxylic acid and ethyl 4-(4-amino-5)-thoxycarbonyl (thiophen-2-yl)-3,5-dimethyl-1H-pyrrole-2-carboxylate have been developed by step reactions. 4-(5-Carboxythiophen-2-yl)-3,5-dimethyl-1H-pyrrole-2-carboxylic acid is the most promising for the study of the growth-stimulating activity on grain seeds.
Experimental part. Using ethyl 4-acyl-3,5-dimethyl-1H-pyrrole-2-carboxylate and ethyl 5-acetyl-2,4-dimethyl-
1H-pyrrole-3-carboxylate as starting compounds 4-(5-carboxythiophen-2-yl)-3,5-dimethyl-1H-pyrrole-2-carboxylic and 5-(5-carboxythiophen-2-yl) 2,4-dimethyl-1H-pyrrol-3-carboxylic acid were obtained. By the action of the Wilsmeier-Haack reagent on the latter the corresponding pyrroles with the chlorvinylcarbaldehyde fragment were isolated; their post-cyclization with ethyl ester of thioglycolic acid and the subsequent hydrolysis leads to the formation of thienylpyroldicarboxylic acids. The study of the physiological activity of the compounds synthesized was performed on seeds of different varieties of wheat and barley.
Conclusions. By means of sequential reactions the polysubstituted thienylpyrrolcarboxylic acids previously unknown and their esters have been synthesized. The features of the study of these compounds as plant growth
stimulants have been revealed.

The synthesis of new N, N`-disubtituted 5-spiro-2,4,6-trihydropyrimidinetriones by ring-closing metathesis reactions has been presented in this work. Starting compounds for obtaining of spirocycles (5,5-diallyl-1,1-dioxythiolanyl-2,4,6-trihydropyrimidinetriones) have been synthesized by two pathways, one of them is condensation of carbamides with malonic acid in the presence of dehydrating agents, whereas the other path consists in the condensation of dicyanodiamide with diallylcyanoacetic ester in the presence of sodium alkoxide, and the resulting products are subjected to alkylation with the following acid hydrolysis. It has been found that imidazolidine containing the isopropoxybenzylidene ruthenium complex is the most suitable for carrying out of ring-closing metathesis reactions since it has the high thermal stability; it allows to obtain the target products with a high yield due to carrying out these reactions at the higher temperatures. The preliminary computer prognosis of the biological activity of new 1,1-dioxythiolan derivatives with the help of PASS (Prediction of Activity Spectra for Substances) programme has shown that some of these compounds can be ATPase proteasome inhibitors. Moreover, new spirocyclopenten containing derivatives may be promissing as precursors for obtaining of biologically active substances.

Glycosylation of aliphatic and aromatic α,ω-diols by the oxazoline method and by peracetylated α-D-glucosaminylchloride in the presence of zinc chloride and co-promoters (quaternary ammonium salts or trityl chloride) have been investigated. The highest yield of bis-glucosaminides in the conditions of oxazoline synthesis (the solvent is dichloroethane, the temperature of the reaction mixture is ~100°C, catalytic quantities of p-toluenesulfonic acid) has been observed for octane-1,8-diol. The products of monoglycosylation of butane-1,4-diol and dodecane-1,12-diol have been also obtained. The influence of the nature of a со-promoter has been studied on the model glycosylation reaction of octane-1,8-diol with peracetylated α-D-glucosaminylchloride in reflux dichloromethane (the ratio of glycosyl-acceptor : glycosyl-donor : zinc chloride : quaternary ammonium salt = 1 : 2,5 : 2,5 : 2,5). The best yields of dimeric glycoside have been obtained using tetrabutylammonium bromide. Increase of the amount of zinc chloride up to 1.5 equivalents in relation to the glycosyl donor has not led to significant changes of the reaction product yield. The yields of bis-glycosylation have been increased using peracetylated α-D-glucosaminylchloride as a glycosyl-donor for all aglycones. The corresponding mono- and bis-glucosaminides of 2,2’-(1,2-phenylenedioxy)diethanole have been synthesized by glycosylation in these conditions. The structure of the glycosides synthesized has been proven by 1H-NMR-spectroscopy.

With the purpose of further search of biologically active substances among 5-(2-, 3-, 4-methoxyphenyl, 3,4,5- trimethoxyphenyl)-3-thio-1,2,4-triazoles and their derivatives 10 new compounds have been obtained. Acetonitrilothio- 1,2,4-triazoles have been synthesized by alkylation of 5-(2-, 3-, 4-methoxyphenyl and 3,4,5-trimethoxyphenyl)- 3-thio-1,2,4-triazoles with halogenonitriles; the primary computer pharmacological screening has shown that the class of compounds mentioned can show such types of the pharmacological activity as antitumor, antiinflammatory and antioxidant ones. Alkylation of 5-R-1,2,4-triazole-3-thiols has been carried out in the medium of anhydrous alcohol or aprotic solvents. It has been found that replacement of the alcoholic solvent by the aprotic one increases the quantitative yield of 5-R-1,2,4-triazol-3-thioacetonitrile; in aprotic solvents the presence of impurities of alkaline hydrolysis products is not practically observed. Iminoethers of 2-(5-(2-, 3-, 4-methoxyphenyl and 3,4,5-trimethoxyphenyl)-1H-1,2,4-triazole-3-ylthio)acetatic acids have been synthesized by saturation of 2-(5-(2-, 3-, 4-methoxyphenyl and 3,4,5-trimethoxyphenyl)-1H-1,2,4-triazol-3-ylthio)acetonitriles with the flow of dry in the alcoholic medium when constant cooling the reaction mixture to –5ºC. It has been found by the method of HPLC/DAD-MS that the qualitative yield of the target product depends on the maintenance of the temperature mode of the reaction mixture. The structure and individuality of the molecules of the substances synthesized have been proven by the method of 1H NMR-spectroscopy and HPLC/DAD-MS.

The one-step method for preparation of 6-(1H-benzimidazol-2-yl)-5-methylthieno[2,3-d]pyrimidin-4(3H)-ones by interaction of 5-methyl-4-oxo-3,4-dihydrothieno[2,3-d]pyrimidine-6-carboxylic acid with ortho-pnenylediamines using 1,1’-carbonyldiimidazole as a coupling-reagent has been developed. The procedure proposed allows to obtain easily the target products using common reagents and solvents; and it also requires the simple isolation methods. The selectivity of 6-(1H-benzimidazol-2-yl)-5-methylthieno[2,3-d]pyrimidin-4(3H)-one interaction with benzyl chlorides in DMF – K2CO3 conditions has been studied using the NOESY spectroscopic method and alternative synthetic approaches; it has been determined that the reaction occurs at position 3 of the thieno[2,3-d] pyrimidine system. The study of the antimicrobial activity by the agar diffusion method for the compounds obtained has shown that 6-(1H-benzimidazol-2-yl)-3-benzyl-5-methylthieno[2,3-d]pyrimidin-4(3H)-ones reveal the antimicrobial activity against the strains of Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa; while the compound with unsubstituted position 3 appeared to be inactive against these strains of microorganisms. However, this compound exhibited the higher inhibitory activity against the Candida albicans fungi.

The review systematizes the theoretical and experimental data concerning methods of synthesis of condensed thiazolopyridines, which at present have been insufficiently studied, the prospects for their application in the directed synthesis of new physiologically active substances. The recent developments in their pharmacology have been also analyzed. The available methods for the synthesis of condensed thiazolopyridines can be divided into two fundamentally different approaches. The first approach is based on annelation of the thiazolidine or thiazole cycle to the pyridine ring, and the second one use pyridine derivatives as starting materials; their functional groups make it possible to change the pyridine ring. Methods for obtaining thiazolopyridines using solid media carriers, and their synthesis with domino reactions deserve a particular attention. Generalization of the scientific data published confirms that the condensed thiazolopyridines exhibit various biological effects. In particular, they are characterized by analgesic, anti-inflammatory, antimicrobial, antioxidant and antifungal activities. Due to the inhibitory action on integrally linked kinase the specified class of compounds can eliminate the hyperproliferative disorders in the living organisms. It has been found that these derivatives exhibit the antidiabetic, antibacterial and anti-tuberculosis action. It is known that derivatives of thiazolopyridines have shown a positive effect in the treatment of sexual dysfunction. Thiazolopyridine derivatives containing the α-amino phosphonate residue at 2 position of the basic heterocycle exhibit a significant anticancer effect.

The syntheses of 3-fluoro-1,8-naphthalimide and 3-fluoro-1,8-naphthalic anhydride from 3-nitro-1,8-naphthalimide have been described. 3-Nitro-1,8-naphthalimide can be obtained by nitration of naphthalimide with sodium nitrate in sulfuric acid. Stability of naphthalimides under acidic and alkaline conditions makes 3-substituted naphthalimides more suitable synthones for further functionalization compared to the corresponding 3-substituted naphthalic anhydrides. The best yield of 3-fluoro-1,8-naphthalimide was achieved through the following sequence: 1) nitration of naphthalic anhydride to 3-nitronaphthalic anhydride by sodium nitrate in the concentrated sulfuric acid; 2) ammonolysis of 3-nitronaphthalic anhydride to 3-nitronaphthalimide with aqueous ammonia; 3) reduction of 3-nitronaphthalimide to 3-amino-naphthalimide with sodium dithionite solution in aqueous ethanol; 4) preparation of 3-fluoronaphthalimide by diazotization of 3-aminonaphthalimide and subsequent thermal decomposition of the corresponding tetrafluoroborate. Nitration of naphthalic anhydride makes it possible to avoid the problem of poor solubility of naphthalimide in sulfuric acid. Subsequent reactions are conveniently carried out with naphthalimide derivatives, thus avoiding the difficulties encountered in isolating of 3-aminonaphthalic anhydride that can undergo a polymerization reaction. The new protocol is more efficient than the preparation route previously described leading to 3-substituted naphthalic anhydrides and naphthalimides by virtue of the substitution reaction at C-4 of acenaphthene followed by oxidation.

Modification of the spiro-2-oxindole skeleton due to introduction of pharmacophores of the known biologically active substances is a productive way for searching and creating new biologically active molecules with the non-planar structure.

Aim. To synthesize spiro-2-oxindole derivatives of pyrrolidine-3,4-dicarboxylic acid imides with residues of biogenic sulfur-containing α-amino acids and study their anti-hypoxic activity.

Results and discussion. Using a three-component one-pot reaction of isatin with sulfur-containing α-amino acids and maleimides a number of new spiro-imides, including 4’-R4-5’-alkylthio-S-R3-spiro[1-R1-5-R5-3H-indole-3,2(1’H)-pyrrolo[3,4-c]pyrrole]-2,3’,5’(1H,2’aH,4’H)-triones 6a-s, was synthesized with the yields of 55-92 %. The structure and the composition of the compounds synthesized are consistent with the results of X-Ray, elemental analysis, mass and NMR-spectra. It was found that only two of the eight possible enantiomers of spiro-imides were formed. Spiro-imide with a methionine residue in the dose of 10 mg/kg was the most active, and increased the life expectancy in rats with respect to the control group by 33.7 % on average. Against the background of acute asphyxia the preventive administration of piro-imide with a methionine residue in the dose of 5 mg/kg was the most effective; it increased the duration of the bioelectric activity of the heart by 12.1 %.

Experimental part. The synthesis of compounds was performed using a three-component condensation in the alcoholic-aqueous medium. The methods of X-Ray, 1H, 13C NMR-spectroscopy, and mass spectrometry were used. The study of the antihypoxic activity was carried out on models of acute normobaric hypoxic hypoxia with hypercapnia and acute asphyxia in male rats of the Wistar line. The antihypoxic effect was assessed by the bioelectric activity of the heart.

Conclusions. An effective approach to the synthesis of 4’-R4-5’-alkylthio-S-R3-spiro[1-R1-5-R5-3H-indole- 3,2’(1’H)-pyrrolo[3,4-c]pyrrole]-2,3’,5’(1H,2’aH,4’H)-triones has been developed; among them a compound with a moderate antihypoxic activity has been found.

The article describes the method of synthesis of a new type of pyrazolo[3,4-e][1,4]diazepin-4-ones substituted in position 7 by fragments of thioalkane carboxylic acids. The literature reference considers the synthetic and biological studies of heterocyclic compounds with exo-functionalized fragments of thioalkan carboxylic acids and it substantiates the expediency of our investigation. The results of the research are development of an effective one pot method for the target compounds, which is based on the intramolecular cyclization of 5-amino-N-(2,2-dialkyloxyethyl)pyrazole-4-carboxamides in the solution of formic acid with thioalkan carboxylic acids. The synthesis of the starting 5-aminopyrazolo- 4-carboxamides has been performed by condensation of 2-cyano-N-(2,2-dimethoxy)-3-dimetylaminoacryl(croton) amides with alkyl hydrazines or hydrolytic cleavage of 5-(2,2-dietoxyethyl)-1,5-dihydropyrazolo-4Н-[3,4-d]pirimidin- 4-ones. The scheme of this reaction proposed involves the intramolecular cyclocondensation with the initial formation of the corresponding 7-hydroxy-5,6,7,8-tetrahydropyrazolo[3,4-e][1,4]diazepin-4(1H)-ones, and further replacement of the hydroxyl group for the carboxyalkylthiol residue in the acidic medium. The structure of the compounds obtained has been proven using the methods of IR-, NMR 1H 13C-spectroscopy, mass-spectra and elemental analysis. The substantial evidence of the diazepine cycle formation is the presence of multiplets of protons H6 in the range of 3.16- 3.50 ppm and multiplets of protons H7 in the range of 4.89-5.17 ppm in the 1Н NMR spectra.

One of the most convenient methods for obtaining ethyl of N-substituted 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylates and their tricyclic analogues at present is condensation of the corresponding anilines with triethyl methanetricarboxylate. In spite of the fact that there are many methods describing the successful performance of this reaction in conditions of laboratory, but unfortunately, all of them appeared to be completely unusable for large production for a variety of reasons. The study of quality of the esters of 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acids by HPLC has shown that all of them contain from 2.4 to 5.6% of specific admixtures of 4-hydroxy-1,2-dihydroquinolin- 2-ones. In laboratory conditions these amounts can be neglected, but for industrial manufacture they can turn into great losses. The source of admixtures of 4-hydroxy-1,2-dihydroquinolin-2-ones appearing in crude esters can be only the esters themselves. It is obvious that ester grouping is partially destroyed not in the process of separation of the final products, but during the course of the basic reaction. It has been experimentally proven that the cause of contamination of the target products with the admixtures of the corresponding 4-hydroxy-1,2-dihydroquinolin-2-ones is water, which is present in reagents. Applying the principles of «green chemistry» the alternative for carrying out the syntheses of ethyl 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylates adapted for industrial manufacture has been suggested on the basis of N-substituted anilines and triethyl methanetricarboxylate.

By alkylation of the products of diethyl 3-methyl-5 {[(methylthio)carbonothioyl]amino}-2,4-thiophenedicarboxylate interaction
with benzylamines the novel derivatives of ethyl 5-methyl-2-(alkylthio)-4-oxo-3,4-dihydrothieno[2,3-d]pyrimidine-6-carboxylates have been obtained. It has been found that the signal of the CH2-group adjacent to the nitrogen atom in position 3 of thieno[2,3-d]pyrimidine system is always observed in the range of 5.35-5.40 ppm, while the position of the signal of methythylene-group connected with the sulfur atom much depends upon the structure of the radical attached to this group. IR-spectra of all the compounds contain the intensive С=О stretching band at 1721-1678 cm-1; the spectra of the compounds with amide function contain bands of stretching N–H of 3280-3263 cm-1, while nitriles have the band of stretching C≡N vibrations near 2250 сm-1. It has been determined that all of the compounds are mostly active against the strain of Candida aibicans fungi. The most resistant microorganism was found to be the strains of Staphylococcus aureus. The only exception is the derivative modified with the thioacetic acid residue in position 2 and unsubstituted benzyl in position 3, which appeared to be highly active against Staphylococcus aureus strain. Amides of thioactetic acid modified in position 3 with 3,4-dichlorobenzyl substituent and thioacetamide substituents in position 2 are active against Pseudomonas aeruginosa, as well as the compound, which contains 3-chlorobenzyl substituent in position 3 and p-chlorobenzotiol substituents in position 2 of thieno[2,3-d]pyrimidine.

Aim. To synthesize a series of hexamethylene-N-maleinimidospiroindole-3,3’-pyrrolo[3,4-c]pyrrole derivatives, study the antimicrobial activity of the compounds synthesized and compare their antimicrobial activity with the antimicrobial activity of the bis-analogs previously synthesized.
Materials and methods. The methods of organic synthesis, instrumental methods for determination of the molecular structure of organic compounds, agar well diffusion method were used.
Experimental part. The interaction of isatins with a-amino acids and 1,6-bismaleinimidohexane in the equimolar ratio led to formation of 1′-(hexamethylene-N-maleinimido)-2a′,5a′-dihydro-1′H-spiroindol-3,3′-pyrrolo[3,4-c] pyrrol-2,2′,6′(1H,3′H,5′H)-trion derivatives. The structure of the compounds synthesized was reliably proven by the instrumental methods. Data of the microbiological screening showed a high level of the antimicrobial activity against Staphylococcus aureus and Candida albicans fungi.
Conclusions. It has been determined that the three-component condensation reaction of isatins with α-amino acids and 1,6-bismaleinimidohexane in the equimolar ratio is an efficient synthetic method of 1′-(hexamethylene-N-maleinimido)-2a′,5a′-dihydro-1′H-spiroindol-3,3′-pyrrolo[3,4-c]pyrrol-2,2′,6′(1H,3′H,5′H)-trion derivatives, which reveal a high level of the antimicrobial activity against Staphylococcus aureus and Candida albicans fungi. 1’-(Hexamethylene-N-maleiimido)-5’-methyl-2a’,5a’-dihydro-1’H-spiroindol-3,3’-pyrrolo[3,4-c]pyrrol-2,2’,6’(1H,3’H,5’H)-trione has shown the highest antimicrobial activity among derivatives of hexamethylene-Nmaleinimidospiroindol- 3,3’-pyrrolo[3,4-c]pyrrols.

Cholinesterase inhibitors can be used for treatment of neuropsychiatric symptoms and functional impairments in neurodegenerative pathologies such as Alzheimer’s and Parkinson’s diseases.
Aim. To synthesize and assess the inhibitory activity of adamantyl-containing 5-substituted N-benzyl and N-phenacylthiazolium salts against butyrylcholinesterase and acetylcholinesterase.
Results and discussion. The synthesis of 3-aroylmethyl- and 3-arylmethyl-5-(2-acyloxyethyl)-4-methylthiazolium salts included preparation of 5-acyloxyethyl thiazole derivatives by the reaction of 5-(2-hydroxyethyl)-4-methyl-1,3-thiazole with the corresponding adamantoyl- or adamantylacetyl chlorides. The derivatives of 5-acyloxyethyl thiazole were quaternized in the reaction with benzyl or phenacyl halides. The studies in vitro have shown that the compounds synthesized inhibit butyrylcholinesterase with IC50 values in the micromolar range. Some of them exhibited selectivity over acetylcholinesterase. The molecular docking was performed for understanding the mechanisms of the enzyme-inhibitor complex formation.
Experimental part. The synthesis of the intermediate and target compounds was carried out by the classical methods. The structures of compounds were proven by NMR 1H-spectroscopy and elemental analysis. The methods of enzymatic kinetics were used for determination of the inhibitory effects of the compounds synthesized. Calculations by molecular docking were carried out using Autodock 4.2 program.
Conclusions. 3-Aroylmethyl- and 3-arylmethyl-5-(2-acyloxyethyl)-4-methylthiazolium salts with adamantylcontaining substituents in position 5 can selectively inhibit butyrylcholinesterase compared to their effect on acetylcholinesterase.

Arylmethyliden derivatives of 2,2-dimethyl-1,3-dioxane-4,6-dione; Meldrum`s acid; 6,7-dihydro-7-aryltetrazolo [1,5-a]pyrimidin-5(4H)-ones; synthesis; pharmacological activity
Cyclocondensations of 1H-tetrazol-5-amine with methylcinnamates, arylmethyliden malonic acids and arylmethyliden derivatives of 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum`s acid) proceed regioselectively and lead to formation of 7-aryl-6,7-dyhidrotetrazolo[1,5-a]pyrimidin-5(4H)-ones. The direction of cyclization corresponds to the interaction of the carbon atom in β-position of the unsaturated carbonyl compounds with the endocyclic nitrogen atom and the carbonyl group with amino group in the aminoazole molecule. Compounds of the isomeric structure in any of the experiments have been not identified. The structures and composition of the newly synthesized tetrazolo[1,5-a]pyrimidin-5(4H)-ones have been confirmed by elemental analysis, infrared spectroscopy (IR), nuclear magnetic resonance on protones (1H NMR) and mass spectra data. Virtual screening of 7-aryl-6,7-dihydrotetrazolo[1,5-a]pyrimidin-5(4H)-ones carried out using the PASS programme for 780 types of the pharmacological action has demonstrated that it is expedient to test these compounds by their analgesic and anti-inflammatory activity, as well as as potential agents for the treatment of heart failure.

Calix[4]arene are known to be a promising scaffold for designing inhibitors of protein tyrosine phosphatases.
In this work calix[4]arene mono- and bis-α-hydroxymethylphosphonic acids have been tested in vitro for the inhibitory activity against some therapeutically important protein tyrosine phosphatases. The results obtained have shown that these macrocyclic compounds can inhibit CD45, PTP1B, and SHP2 with IC50 values in the micromolar range. At the same time the inhibitors have demonstrated lower activity toward other protein tyrosine phosphatases such as TC-PTP and PTPβ. It has been found that mono-substituted calix[4]arene is more potent inhibitor of CD45 than the bis-substituted one and shows about 2-15 fold selectivity over TC-PTP, PTPβ, SHP2 and PTP1B. Model 4-hydroxyphenyl-α-hydroxymethylphosphonate displays at least one order lower activity than the phosphonate derivatives of calix[4]arene. Thus, the combination of a macrocyclic platform and α-hydroxymethylphosphonate group is essential for the inhibition activities of these compounds. Computer-simulated docking studies have been performed using AutoDock 4.2 programme by the example of PTP1B. The data obtained indicate that the inhibitors can bind in the active site of the enzyme. To clarify the inhibition mechanism the possible enzyme-inhibitor complexes have been considered using several crystal structures of PTP1B and all stereoisomeric forms of the inhibitors.

Precarbene and metalcarbene compounds of a series of imidazole have been synthesized to study their antimicrobial activity. Calix[4]arene imidazolium salts 3,4a,b have been obtained from the corresponding chloromethyl derivatives of calix[4]arenes and N-substituted imidazoles in dimethylformamide or tetrahydrofuran, and salt 5 – from p-xylylenediimidazoles and 1-bromoadamantane in o-dichlorobenzene. Monocarbene complexes of palladium 8a-c, copper(I) 8d and biscarbene complexes of nickel 9a and cobalt 9b have been synthesized by the direct interaction of stable carbenes with transition metal salts or by the analogous reactions in situ in tetrahydrofuran. The NMR spectra data of the compounds synthesized are given. The most characteristic signals of the carbenoid carbon atoms are detected in the 13С NMR spectra of complexes 8a-d, 9a in the range of 165-178 ppm. A high antimicrobial activity has been found for carbenoid salts 4a,b, 5 on the test-culture of M. Luteum. It corresponds to the minimal bacteriostatic concentration (MBsC) of 15.6 mkg/mL and the minimal bactericidal concentration (MBcC) of 62.5 mkg/mL for compound 2. The higher activity has been found for carbene complexes of nickel 9a and cobalt 9b on the test-culture of M. luteum (MBsC is 7.8 mkg/mL and MBcC is 15.6 mkg/mL), and the highest 9b on the test-cultures of M. luteum and C. tenuis (the minimal fungistatic concentration is 1.9 mkg/mL and the minimal fungicidal concentration is 3.9 mkg/mL).

Aim. To study the qualitative composition, the quantitative content of catechins in green tea leaves and compare the data obtained with those evaluated by spectrophotometry.
Materials and methods. Green tea leaves used for the analysis were collected in Anhui Province, China. The extract for the HPLC analysis was obtained by the maceration method with 60 % ethanol twice in the raw material/extractant ratio of 1 : 20. In the case of the spectrophotometric analysis, green tea leaves were extracted with 70 % ethanol twice by the maceration method in the raw material/extractant ratio of 1 : 20. The analysis of the extract from green tea leaves was performed by high performance liquid chromatography using a Prominence LC-20 Shimadzu chromatographic system (Japan) with a SPD-20AV spectrophotometric detector, an Agilent Technologies Microsorb-MV-150 column (reversed phase, C18 modified silica gel, length – 150 mm, diameter – 4.6 mm, particles size – 5 μm). Substances in the extract were identified by comparing the retention time and the spectral characteristics of the test substances with the same characteristics of the reference standards. Spectrophotometric measurements were carried out using a UV-1000 single beam spectrophotometer (China) with the pair of S90-309Q quartz square cells.
Results and discussion. Using high performance liquid chromatography 5 catechins were identified.
Among them epigallocatechin-3-O-gallate (10.85 %) predominated, while catechin (0.61 %) had the lowest concentration. The total amount of catechins in green tea leaves was 30.56 and 24.79 % by HPLC and spectrophotometry, respectively. The F- and t-tests showed that there was no significant difference between the results of HPLC and spectrophotometry.
Conclusions. The qualitative composition and the quantitative content of catechins have been determined in the extract from green tea leaves by high performance liquid chromatography and spectrophotometry. Both HPLC and spectrophotometric methods can be used to determine the total catechin content in green tea leaves. The high content of catechins makes the extract promising for further study and creation of new herbal medicinal products and dietary supplements. The results obtained will be used for standardization of green tea leaves and for future pharmacological research of its extract.

 Organic acids are a large group of biologically active compounds that perform important functions in the plant organism. Moreover, all plants, regardless of the species and family, contain organic acids to a small or large extent as organic acids belong to intermediate metabolites arising from the oxidation of proteins and amino acids, fats and carbohydrates.
Aim. To validate the method of alkalimetry proposed with potentiometric detection of the end-point for the quantitative determination of free organic acids in raspberry leaves.
Results and discussion. The method proposed was validated according to the International Conference on Harmonization (ICH) guidelines. The linearity was in the concentration range of 40 – 200 % (r² = 0.9991). The percentage of recovery was found to be in the range of 98.77 – 102.48 %. The repeatability and intermediate precision were 1.58 % and 1.74 %, respectively. The method is accurate and reliable, with the relative standard deviation of less than 2 %.
Experimental part. Leaves of raspberry were collected in the Kharkiv region during the period of full ripening. A Hanna 2550 pH-meter with a HI 1131P potentiometric electrode was used for alkalimetric titration of free organic acids. The titration was carried out using a microburette with Class A accuracy.
Conclusions. The alkalimetry method for the quantitative determination of free organic acids in raspberry leaves has been proposed and validated according to the following parameters: specifcity, linearity, accuracy, repeatability, intermediate precision, robustness. It has been confrmed that the method is simple, reliable, accurate and cost-effective.
Key words: raspberry; leaves; free organic acids; alkalimetry; validation

Aim. To synthesize 5-ene-4-thiazolidinones containing heterocyclic rings in the molecule as potential anticonvulsants, and screen their anticonvulsant activity on a model of pentylenetetrazole (PTZ) seizures.
Results and discussion. A straightforward and convenient synthesis of novel 5-ene-derivatives of thiazol/oxazole-bearing 4-thiazolidinones as possible anticonvulsant agents was performed. Compounds were characterized using methods of spectral analysis (¹H NMR and LC-MS). 5-Chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde underwent the aminolysis on a chlorine atom by a molecule of monoethanolamine (MEA) in the Knoevenagel reaction with thiazole/oxazole-bearing 4-thiazolidinones. The preliminary screening of the anticonvulsant activity was performed for the compounds synthesized on the model of PTZ-induced seizures, and active derivatives were identified.
Experimental part. Commercially available 2-aminothiazole and 5-methylisoxazol-3-amine were used as starting compounds for the synthesis of 2-chloro-N-(hetaryl)acetamides. The latter were transformed into thiazole/oxazole-bearing 4-thiazolidinones by the treatment with ammonium isothiocyanate. Modification at C5 position of the heterocycles synthesized was performed by the Knoevenagel reaction with aromatic/heteroaromatic aldehydes and MEA as a catalyst (either equimolar or 0.1 mol% amount) in the ethanol medium. The structure of novel derivatives was confirmed by ¹H NMR and LC-MS spectra. The anticonvulsant activity of all derivatives synthesized was studied in vivo on the model of PTZ-induced seizures. Latency of the seizures, the number of clonic-tonic seizures in one mouse, the percent of animals with clonic and tonic seizures, the duration of the seizure period, and the lifetime of the animals before death were evaluated and calculated.
Conclusions. The results obtained are promising for further design of potential anticonvulsants among oxazole-bearing 4-thiazolidones with the possible mechanism of the anticonvulsant action through the GABA-ergic impact and inhibition of the prostaglandin and leukotriene synthesis.

Aim. To determine the quantitative content of the main groups of biologically active substances (BAS) in batches of Viburnum opulus fruits using pharmacopeial methods for their subsequent use in the standardization of the plant raw material.
Materials and methods. For the study, 6 batches of air-dried Viburnum opulus fruits crushed to a particle size of 1 – 2 mm and harvested in different regions of Ukraine in the mass fruiting phase in October-November 2020 were used. The quantitative determination of polyphenols and tannins was performed using the spectrophotometric method at a wavelength of 760 nm calculated with reference to pyrogallol and dried substance. The total amount of hydroxycinnamic acids was determined according to the method of the SPhU (State Pharmacopoeia of Ukraine) 2.0 described in the monograph “Kidney Tea^N” calculated with reference to rosemary acid. The total amount of organic acids was determined by the titrimetric method according to the method of the monograph of the SPhU 2.1 “Rose hips^N” calculated with reference to malic acid.
Results and discussion. The quantitative content of polyphenols (calculated with reference to pyrogallol and dried substance) in batches of Viburnum opulus fruits varied by about 1.4 times from 1.74 ± 0.01 % to 2.36 ± 0.01 %. According to the results obtained, the quantitative content of tannins (calculated with reference to pyrogallol and dried substance) in batches of Viburnum opulus fruits varied by 1.7 times from 0.73 ± 0.01 % to 1.23 ± 0.01 %. The quantitative content of the total amount of hydroxycinnamic acids calculated with reference to rosemary acid in batches of Viburnum opulus fruits ranged by 1.2 times from 3.96 ± 0.01 % to 4.73 ± 0.01 %. The quantitative content of the total amount of organic acids calculated with reference to malic acid in batches of Viburnum opulus fruits fluctuated more than 1.3 times from 6.80 ± 0.01 % to 9.08 ± 0.01 %.
Conclusions. The quantitative content of the main groups of biologically active substances has been determined in 6 batches of Viburnum opulus fruits harvested in different regions of Ukraine using pharmacopoeial methods: polyphenols (varied by 1.4 times), tannins (varied by 1.7 times), the total amount of hydroxycinnamic (varied by 1.2 times), and the total amount of organic acids (varied by 1.3 times) calculated with reference to dried substance. The content of the groups of biologically active substances in batches of Viburnum opulus fruits slightly correlates with the place of the raw material harvesting. Thus, the selected methods of the SPhU 2.0 are quite suitable for determining the quantitative content of polyphenols, tannins and of the total amount of hydroxycinnamic and organic acids in batches of Viburnum opulus fruits; they can be used in further studies to standardize the raw material.

Aim. To analyze and summarize the synthetic potential of 1,2,3-triazole-4(5)-amines as efficient building blocks in the synthesis of triazolo-annulated pyridine, azine and azepine systems.
Results and discussion. Original literature sources revealing the synthetic potential of 4(5)-amino functionalized 1,2,3-triazoles as convenient and available building blocks for the preparation of triazolo-annulated pyridines, azines and azepines were analyzed and systematized. Condensation of 1,2,3-triazole-4(5)-amines with methylene active compounds was shown to be a powerful tool for the synthesis of versatile triazolo[4,5-b]pyridines. In turn, the cyclocondensation based on 5-amino-1,2,3-triazole-4-carboxylic acids and their structurally modified derivatives was proven to be a general way for obtaining a number of triazolo[4,5-d]pyrimidine systems. Few representatives of triazolo-annulated pyridazines, 1,3-oxazines and 1,3-thiazines were synthesized by the intramolecular cyclization of the corresponding 4-aryl(carboxy-, aminomethyl)-5-amino-1,2,3-triazoles. The cyclocondensation involving 4,5-diamino-, 4-carbofunctionalized 5-amino-1,2,3-triazoles and 4-amino-5-thiocarboxamido-1,2,3-triazoles was successful for the construction of di-, oxa- and thiazepino-annulated triazoles.
Conclusions. The analysis, systematization and summary of the literature regarding the synthetic potential of 1,2,3-triazole-4(5)-amines conclusively demonstrate that these structures are easily available and convenient molecular blocks for the construction of triazolo-annulated pyridine, azine and azepine systems that are important for synthetic and biomedical research.

Aim. To synthesize aliphatic and aromatic derivatives of salt carbenoid compounds of the series of imidazole, benzimidazole, pyridine, pyrimidine and 1,3,4-oxadiazole containing fluorophenyl, cetyl or adamantyl substituents, and study their antimicrobial (antibacterial and antifungal) activities.
Results and discussion. New derivatives of heterocyclic carbenoid salts and zwitterions based on the imidazole, benzimidazole, pyridine, pyrimidine and 1,3,4-oxadiazole heterocyclic systems containing fluorophenyl, cetyl or adamantyl substituents were synthesized. For this purpose, reactions of cyclization of the corresponding diimines with ethoxymethyl chloride (imidazolium salts), quaternization of the corresponding azoles with cetyl bromide or 1-adamantyl bromide in organic solvents (benzimidazolium, pyridinium and 1,3,4-oxadiazolium salts), cyclization of di(1-adamantylamino)alkanes hydrobromides with the orthoformic ester (4,5-dihydroimidazolium and tetrahydropyridinium salts) were used. Zwitterionic compounds were obtained by the reaction of the corresponding azolium salts with phenyl isothiocyanate in the presence of potassium carbonate. Some macrocyclic and adamantyl substituted heterocyclic compounds showed antifungal and antibacterial activities.
Experimental part. The structure of the compounds synthesized was proven by ¹H and ¹³C NMR spectroscopy methods. The antimicrobial activity was studied out by the agar diffusion method to determine diameters of the growth inhibition zones of microorganisms (bacteria and fungi) and by the method of serial dilutions to determine the minimum inhibitory concentration and minimum bactericidal and fungicidal concentrations.
Conclusions. The synthesis of new heterocyclic carbenoid salts and zwitterions based on the imidazole, benzimidazole, pyridine, pyrimidine and 1,3,4-oxadiazole heterocyclic systems containing fluorophenyl, cetyl or adamantyl substituents has been performed. Compounds of macrocyclic and adamantyl heterocyclic series with antifungal and antibacterial activities have been found. 1,3-Dicetylimidazolium bromide, macrocyclic bis(decylenebenzimidazolium) bromides, azolium-N-phenylthiocarboximides have been proven to be the most active.

Aim. To synthesize hexahydrospiro[cyclopropane-1,10’-pyrido[1,2-c]quinazoline] and 2-λ⁵-benzo[f][1,4,2]diazaphosphepine derivatives – new N-P containing heterocyclic compounds with the 6-azaspiro[2.5]octane fragment.
Results and discussion. A new analog of the powerful electrophilic reagent – “Alder dimer” ‒ was obtained from the interaction of triflic anhydride and spiro(4-cyclopropane) piperidinyl formamide, and further used to synthesize new Nʹ-P^V- and P^III-substituted Νʹ-phenyl, Νʹʹ-hexahydro(azaspiro)octylformamidinium salts – precursors of acyclic N-phosphorylated diamino carbenes with a spiroamine group. It has been shown that acyclic N-phosphorylated diaminocarbenes are transient species affording various products. The structure of the final product is primarily determined by nature of the phosphorus-bearing substituent, namely a phosphoryl or phosphino-group. N-P^V-substituted carbene undergoes a 1,2-phosphorus shift with the formation of (selenophosphoryl)formamidine in a high yield. For N-P^III-substituted carbene a compatible 1,3-H shift also occurs with the formation of an intermediate azomethine ylide converted into a new heterocyclic system – hexahydrospirocyclopropane -1,10’-pyrido[1,2-c]quinazoline. Under the action of acid an unexpected further expansion of the 6-member ring occurs with the formation of a diazepine derivative.
Experimental part. The reaction of Alder reagent with N-P^V-seleno phosphoryl arylamides afforded N-phosphorus substituted formamidinium salts, which are easily reduced to P^III analogues. In addition to the corresponding formamidines, the new N-phosphorylated spiroamine-containing polycyclic system was isolated from the reaction mixture formed by the deprotonation of such salts with a strong non-nucleophilic base.
Conclusions. The Alder reagent approach allows synthesizing precursors of acyclic formamidine carbenes with the spiroamine group. Such carbenes are unstable. By converting these compounds N-P^III-substituted tetrahydropyrimidine and diazaphosphepine derivatives with the 6-azaspiro[2.5]octane fragment have been obtained for the first time.

Much attention is currently paid to the study of the antioxidant properties of various objects – individual antioxidants, dietary supplements, medicines, liquid plant extracts. Antioxidant medicines are widely used as the main or additional correction agents in the treatment of a number of diseases. Therefore, the study and development of procedures for determining the antioxidant activity is a prospective task for today.

Aim. To determine the contribution of different concentrations of ethanol to the level of the antioxidant activity (AOA) of ascorbic acid solutions by the potentiometric method.

Results and discussion. The different ethanol content in the solution had the following percent of the contribution to the value of AOA of ascorbic acid solutions – 1.85, 3.56, 4.89, 6.76, 7.63 % for 20, 40, 60, 80, 96 % ethanol, respectively. The linearity of the procedure was proven in the range from 0.039 to 0.31 mmol/L.

Experimental part. The object of the study was solutions of ascorbic acid prepared using ethanol of different concentrations – 20, 40, 60, 80, 96 %. Potentiometric measurements were conducted by a Hanna 2550 pH meter (Germany) with an EZDO 5010 combined platinum electrode. Weighing was carried out using an АN100 digital analytical balance (AXIS, Ukraine) with d = 0.0001 g. Ascorbic acid was purchased from Sigma Aldrich (≥ 99.0 %), K₃[Fe(CN)₆], K₄[Fe(CN)₆], NaHPO₄, KH₂PO₄ were of analytical grade.

Conclusions. It has been found that ethyl alcohol affects the change of the potential in the electrochemical cell and the level of AOA of ascorbic acid solutions. The percentage of the contribution of different concentrations of ethyl alcohol to the AOA value ranges from 1.85 to 7.63 %. The approach and the formula for calculation that take into account the effect of ethyl alcohol on the final AOA result of the test sample of ascorbic acid in a water-alcohol solutions have been proposed. The results of this study can be used in the pharmaceutical and food industries to determine, assess and control the AOA level of dietary supplements, liquid extracts, tinctures, medicines, and alcoholic beverages.

Virtually unknown in her homeland, Bianka Tchoubar, born in 1910 in Kharkiv, brought about a true paradigm shift in French organic chemistry of the 20th century. Originality of research ideas, scientific rigor and legendary perseverance earned her respect and recognition in the world scientific community. This eccentric Parisian of Ukrainian origin became the first woman to enter the French National Center for Scientific Research (Centre National de la Recherche Scientifique, CNRS) upon its creation in 1939. Bianka Tchoubar’s contribution to the study of reaction mechanisms and salt effects in organic chemistry were of paramount importance, and so were her efforts to present these novel scientific concepts to the audience of French organic chemists through the clear and concise expression of her books. The name of this great Ukrainian researcher may be found in the pages of French organic chemistry textbooks, where the Demjanov ring expansion reaction is called the Demjanov–Tiffeneau–Tchoubar rearrangement. This article aims at presenting the outstanding scientific legacy and turbulent life path of this researcher to the world scientific community.

Aim. To share our experience when working with the Pd-catalyzed hydrogenation and discuss reactions occurred contrary to our expectations, as well as express our vision of the causes for such an unusual reactivity.
Results and discussion. Catalysis is a key technology and among the central themes of both petrochemical and fine chemical industries. Although extremely useful and reliable, it can sometimes astonish researchers. The paper discusses 17 intriguing cases of the catalytic hydrogenation and hydrogenolysis reactions from our practice in the High-pressure Synthesis Laboratory (Enamine Ltd.). All examples presented are characterized by peculiar performance of commercially sourced heterogeneous palladium-containing catalysts (Pd/C or Pd(OH)₂). Thus, some cases were characterized by reduced activity of the catalyst (or even its complete loss), meaning that reaction conditions found before to be suitable for reduction appeared to be “broken”, and we had to search for a new, often harsher reaction setup. Curiously, it is a matter of classical Pd-catalyzed hydrogenations of N⁺–O^– and C=C fragments. Apparently, these results indicate the heterogeneity of commercially available catalysts and are related to their fine internal structure, in particular the surface morphology. Another interesting issue the article deals with is chemoselectivity of the catalytic hydrogenation. Sometimes some reactions led to astonishing results going across theoretical views and expectations. Saturation of benzene rings instead of (or accompanying) debenzylation, breaking of the common order of hydrogenation for compounds containing several aromatic parts with different resonance energies, irreproducible experiment, obtaining of different products under the same conditions, uncommon results of Pd-catalyzed reactions is the list of interesting results, which we observed and discussed in the article. Analyzing the information available in the literature and considering all the results gathered we tend to believe that the presence of impurities of noble metals (Rh, Ru, Pt) in the catalysts used to be a possible reason for these strange findings. The study supports the general idea that commercial palladium catalysts differ in efficiency, resulting in significant differences in selectivity, reaction time, and yields. Elucidating the regularities behind such empirical results is undoubtedly an interesting area of research in the field of catalysis.
Experimental part. All starting compounds exposed to hydrogenation were synthesized in Enamine Ltd. and had purity of not less than 95 %. The palladium-containing catalysts used in the experiment were purchased from 6 commercial sources within 2011 – 2022. The structure and purity of the compounds synthesized were characterized by ¹H NMR spectroscopy, liquid chromatography coupled with the mass spectrometry method, elemental analysis. Chromatographic experiments revealed the purity of all compounds obtained being not less than 95 %.
Conclusions. In the paper we have summarized our experience with the Pd-catalyzed hydrogenation and presented cases of unusual reactivity or unexpected outcomes of the reactions encountered in our practice. In general, complications we faced were of three types: (1) irreproducibility of the procedures most likely as the result of a changeable activity of the catalysts; (2) chemoselectivity issues when two or multireducible functional groups were present in the substrate; (3) undesirable Pd-catalyzed defunctionalization reactions. In turn, these complications led to increase in production costs, loss of time and resources. Therefore, because of this variability in the efficiency of Pd catalysts, far more efforts are required to find out the key differences between commercial sources of Pd catalysts, as well as to create protocols clearly defining the catalytic activity of each batch of the catalyst allowing to identify high-quality catalysts immediately prior to the use without wasting precious time and synthetic materials.