Vol. 16 No. 4(64) (2018)
Published:
2018-12-14
Original Researches
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Domino-reactions of isatins with 5-aminopyrazoles and 2,2-dimethyl-1,3-dioxane-4,6-dione
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.
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The synthesis and physicochemical properties of alkyl-2-(3-thio-5-(1Н-tetrazole-1-yl)methyl-4-R-4Н-1,2,4-triazole-3-yl)ethan(propan,benz)imidates
The synthesis of new biologically active compounds that will replace expensive foreign medicines at the pharmaceutical market of Ukraine is one of the most important directions in development of modern pharmacy and medicine. The synthesis, study of physicochemical and biological properties of new compounds containing 1,2,4-triazole and 1H-tetrazole cores are important tasks of modern synthetic chemistry.
Aim. To synthesize new highly efficient and low-toxic substances, namely alkil-2-((5-(1Н-tetrazole-1-yl)methyl-4-R-1,2,4-triazole-3-yl)thio)etan(propan,benz)imidates, and study physicochemical properties of all compounds synthesized.
Results and discussion. Twelve new compounds have been obtained as a result of synthetic transformations, the structure of compounds synthesized has been confirmed by modern complex of physicochemical methods of analysis (IR-spectrophotometry, 1H NMR-spectroscopy, 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.
Experimental part. As starting materials for the synthesis of alkil-2-((5-(1Н-tetrazole-1-yl)methyl-4-R-1,2,4-triazole-3-yl)thio)etan(propan,benz)imidates the corresponding 2-((5-(1Н-tetrazole-1-yl)methyl-4-R-1,2,4-triazole-3-yl)thio)aceto(propane,benzo)nitriles were used. The synthesis was carried out in the absolute alcohol medium (propanol, butanol, octanol or allyl alcohol) with chloroform.
Conclusions. During synthetic and physicochemical studies the preparative methods for the synthesis of alkil-2-((5-(1Н-tetrazole-1-yl)methyl-4-R-1,2,4-triazole-3-yl)thio)etan(propan,benz)imidates have been developed, the structure of the compounds synthesized has been determined and finally confirmed.
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The synthesis and cyclofunctionalization of (1,3-thiazolidin-2-ylidene)ketones
Aim. To develop a new approach to the design of (1,3-thiazolidin-2-ylidene)ketones and expansion of their synthetic potential as convenient building blocks in the reactions of [3+2]- and [3+3]-cyclization.
Results and discussion. Еlectrophilic intramolecular cyclization (EIC) of N-allythioamides of β-ketoacids using phosphoric acid or iodine is a convenient synthetic method to obtain new (5-methyl- and 5-iodomethyl-1,3-thiazolidine-2-ylidene)ketones. Cyclization of ketones with maleic anhydride leads to derivatives of 2,3-dihydropyrrolo[2,1-b][1,3]thiazole. [3+3]-Cyclocondensation with methyl propiolate and dimethyl acetylenedicarboxylate results in formation of the functionalized [1,3]thiazolo[3,2-a]pyridine derivatives.
Experimental part. (5-Methyl- and 5-iodomethyl-1,3-thiazolidin-2-ylidene)ketones were synthesized from N-allylthioamides using phosphoric acid or iodine in chloroform. (1,3-Thiazolidin-2-ylidene)ketones react with maleic anhydride, methyl acetylenecarboxylate or dimethyl acetylenedicarboxylate resulting in a 2,3-dihydropyrrolo[2,1-b][1,3]thiazole-5(6H)-one and 2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyridine derivatives.
Conclusions. A convenient method of [5-methyl- and 5-iodomethyl-1,3-thiazolidin-2-ylidene]ketones preparation based on the EIC of N-allylthioamides of β-ketoacids has been developed using phosphoric acid and iodine. The (1,3-thiazolidin-2-ylidene)ketones synthesized can be useful in cyclization reactions leading to functional pyrrolo[2,1-b][1,3]thiazole and [1,3]thiazolo[3,2-a]pyridine derivatives.
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The synthesis of derivatives of tetra(hexa)hydro[1,2,3]triazolo-[4,5-e][1,4]diazepines and their acylation
Aim. To study the conditions for reduction of 5-hydroxy[1,2,3]triazolo[4,5-e][1,4]diazepines and develop the method for the synthesis of their tetra- and hexahydroderivatives.
Results and discussion. It has been found that the functional hydroxy and carbonyl groups of 5-hydroxy[1,2,3]triazolo[4,5-e][1,4]diazepines tend to selective reduction with complex metal hydrides, and it has allowed to develop methods for the synthesis of their hydrogenated derivatives and to carry out the acylation of the diazepine cycle.
Experimental part. The selective reduction of the hydroxy group was obtained by the interaction of 5-hydroxy[1,2,3]triazolo[4,5-e][1,4]diazepines with a 2-fold excess of NaBH4 in the boiling isopropanol. It allowed obtaining derivatives of tetrahydro[1,2,3]triazolo[4,5-e][1,4]diazepine-8(3H)-one with the yield of 61-82 %. The complete reduction of the diazepine cycle can be achieved only by using a 5-fold excess of LiAlH4-Me3SiCl hydration system and long-term boiling in THF. It has been shown that the tetrahydroderivatives synthesized with aliphatic carboxylic anhydrides are prone to selective acylation of the N4 diazepine ring atom, while hexahydroderivatives form a product of acetylation at N4 and N6 atoms.
Conclusions. The conditions for the partial and complete reduction of 5-hydroxy[1,2,3]triazolo[4,5-e][1,4]diazepines have been found, convenient methods for the synthesis of tetrahydro- and hexahydroderivatives have been developed, and their directed functionalization by acyl groups has been performed.
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The synthesis, study of 6-((5-phenethyl-4-R-1,2,4-triazole-3-ylthio)pyridyn-3-yl)-(alkyl, heteryl)methanimines and their derivatives
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.
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Development and validation of GLC/FID- and GLC/MS-procedures of secnidazole determination by the methods of additions
Gas-liquid chromatography is widely used in the process of forensic toxicological examinations, but data about application of GLC with flame-ionization and mass-spectrometry detection for secnidazole determination in analytical toxicology are absent.
Aim. To develop GLC/FID- and GLC/MS-procedures for the quantitative determination of secnidazole and carry out step-by-step validation of the procedures developed in the variant of the method of additions.
Results and discussion. The chromatographic conditions has been chosen for secnidazole determination by the method of GLC in two variants of performance with flame-ionization and mass-spectrometry detection with the temperature program changing during the analysis from 70 °C to 250 °C or 320 °C. Retention times for secnidazole are 8.97 min and 11.74 min. To prove the possibility of application of the procedures proposed in further analysis their validation has been carried out in the variant of the method of additions. Such validation parameters as in-process stability, linearity, accuracy and precision have been estimated by model solutions.
Experimental part. The GLC/FID-analysis: HP 6890 Hewlett Packard; НР-1 ø0.32 mm × 30 m, 0.25 μm; thermostat – 70 ºС (3 min), 40 ºС/min to 180 ºС (2 min), 40 ºС/min to 250 ºС (3 min); injector – 280 ºС; detector – 280 ºС; volume rate of a carrier gas (helium) – 1.5 ml/min; split mode – 1 : 2. The GLC/MS-analysis: Agilent 6890N/5973N/7683; НР-5MS ø0.25 mm × 30 m, 0.25 μm; DB-17MS ø0.25 mm × 30 m, 0.15 μm; columns are connected sequentially through Deans switch; thermostat – 70 ºС (2 min), 45 ºС/min. to 210 ºС, 6 ºС/min to 320 ºС (12.56 min); transfer line – 280 ºС; ion source – 230 ºС; quadrupole – 150 ºС; electron impact – 70eV; 40-750 m/z; injector – 250 ºС; splitless mode; inlet carrier gas (helium) pressure: 1st column – 26.06 psi, 2nd column – 19.30 psi.
Conclusions. New procedures for the quantitative determination of secnidazole by the method of GLC/FID and GLC/MS have been developed. Their validation has been carried out, and acceptability for application has been shown.
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Determination of the quantitative content of procyanidins in hawthorn fruits
Aim. To determine the quantitative content of procyanidins in hawthorn fruits.
Results and discussion. It was found that the quantitative content of procianidinsin Crataegus succulentha Sarg. fruits was 1.45 % ± 0.02; C. prunifolia Sarg. – 1.24 % ± 0.05; C. pseudokyrtostila Klok. – 1.15 % ± 0.03; C. leiomonogyna Klok. – 1.28 % ± 0.04; C. arnoldii Sarg. – 1.38 %± 0.02; C. submollis Sarg. – 1.37 % ± 0.03; C. mollis Sarg. 1.48 % ± 0.01.
Ехperimental part. The content of procyanidins was determined by the spectrophotometric method calculated with the reference to cyanidin chloride. The optical density of the test solution was measured at a wavelength of 545 nm. The study was performed on a Thermo Fisher Scientific model EVOVUTION 60S spectrophotometer.
Conclusions. Procyanidins of fruits of 7 nonofficinal species of the genus Crataegus L. have been studied. It has been determined that all samples under research meet the requirements of the SPhU and EuPh by the indicator “Assay for procyanidins”, which should be at least 1 %.
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Application of thin layer chromatography and color tests in the analysis of metronidazole
Metronidazole belongs to the group of antiprotozoal medicines and is a potential object of research in various areas of analytical toxicology.
Aim. To study the metronidazole behavior when developing with color reagents generally accepted and to determine Rf values of metronidazole under chromatographing conditions in the solvent systems generally accepted in forensic toxicology.
Results and discussion. It has been shown that such widely used color reagents as UV-light, iodine vapor, Wagner reagent, acidified iodoplatinate solution can be used for detecting metronidazole on chromatographic plates. Metronidazole gives positive detection results with reagents used in the TLC-screening of extracts from the biological material for substances of basic, acid and neutral nature. It has been proposed to develop metronidazole with the neutral ninhydrin solution, p-dimethylaminobenzaldehyde solution and hydrochloric acid vapors, as well as acidified iodoplatinate solution after keeping the plates in formalin vapors. The chromatographic mobility of metronidazole has been studied in 17 solvents systems; the systems are used as standard mobile phases according to recommendations of the International Association of Forensic Toxicologists for TLC-screening of organic compounds of acid, neutral and basic nature, in the general TLC-screening of organic substances in the Ukrainian forensic toxicological laboratories, and some systems investigated with the purpose of choosing the optimal individual solvents systems for the metronidazole study.
Experimental part. The chromatographic plates Sorbfil® PTLC-IIH-UV and Merck® TLC SILICA GEL 60 were used as thin layers.
Conclusions. The behavior of metronidazole when developing on TLC-plates with two types of a substrate (plastic and glass) and with/without luminophor (or UV-indicator) with commonly used colored reagents has been studied. The Rf values of metronidazole under chromatographing conditions in the standard solvent systems used for TLC-screening of organic compounds of acid, neutral and basic nature have been determined.
