Vol. 17 No. 2(66) (2019)
Published:
2019-06-14
Original Researches
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NH-Polyfluoroalkyl іminophosphonates in the synthesis of α-amino-α-polyfluoroalkyl- γ-oxobutylphosphonic acids
Aim. To develop the preparative method for the synthesis of optically active α-amino-α-polyfluoroalkyl-γ-oxobutylphosphonic acids as new promising chiral building blocks.
Results and discussion. It has been shown that the reaction of NH-polyfluoroalkyl aminophosphonates with acetone in the presence of a catalytic amount of L- or D-proline occurs stereoselectively to give enantiomerically enriched (R)- or (S)-α-amino-γ-oxophosphonates, respectively. The resulting optically active phosphonates were converted into water-soluble α-amino-γ-oxophosphonic acids isolated in the individual form as hydrochlorides.
Experimental part. By the reaction of рolyfluoroacetonitriles with diethyl phosphite in the presence of triethylamine the series of NH-рolyfluoroalkyl іminophosphonates were synthesized. They undergo the prolinecatalysed reaction with acetone to form optically active α-amino-α-polyfluoroalkyl-γ-oxobutyl phosphonates. The latter were converted into the corresponding phosphonic acids by the reaction with hydrogen chloride. The structures of the compounds synthesized were confirmed by analytical and spectral NMR (1Н, 13С, 19F, 31Р) methods.
Conclusions. Based on the proline-catalyzed reaction of NH-рolyfluoroalkyl іminophosphonates with acetone the preparative
synthesis method for new chiral building blocks – α-amino-α-polyfluoroalkyl-γ-oxobuthylphosphonates and phosphonic acids has been developed. -
The synthesis and antimicrobial activity of 5-aroxy-2,6-dihydro-1H-pyrrolo[3,4-d] pyridazine-1-ones
Aim. To develop an effective method for the synthesis of 5-aroxy-2,6-dihydro-1Н-pyrrolo[3,4-d]pyridazine-1-ones as promising objects to be investigated in the context of their antimicrobial activity.
Results and discussion. It has been found that ethyl 4-formyl-5-chloro-1Н-pyrrole-3-carboxylates can be used as convenient source substrates for building 5-aroxy-2,6-dihydro-1Н-pyrrolo[3,4-d]pyridazine-1-one systems. MBsC (MFsC) and MBcC (MFcC) of the pyrrolo[3,4-d]pyridazine-1-ones synthesized were within the range
of 31.25-125 μg/ml.
Experimental part. The two-stage synthesis of 5-aroxy-2,6-dihydro-1Н-pyrrolo[3,4-d]pyridazine-1-ones was performed. The chemical composition and the structure of the compounds synthesized were confirmed by chromatography-mass spectra, IR- and NMR 1Н (13С) spectra. The screening of the antimicrobial activity using the micromethod of the double series dilutions in the liquid nutrient medium allowed identifying compounds with a moderate activity.
Conclusions. A preparative convenient synthesis of 5-aroxy-2,6-dihydro-1Н-pyrrolo[3,4-d]pyridazine-1-ones has been developed. This method assumes the nucleophilic substitution of the chlorine atom in ethyl 4-formyl-5-chloro-1Н-pyrrole-3-carboxilates with an aroxyl fragment followed by the subsequent pyridazinoanelination of
ethyl 5-aroxy-4-formyl-1Н-pyrrole-3-carboxylates by hydrazine hydrate. The results of the antimicrobial activity of the substances synthesized substantiate the feasibility of further in-depth studies in this area. -
The synthesis of polisubstituted thienylpyrroles and the study of their activity as plant growth stimulators
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. -
Acetylcholinesterase inhibitors with a thiazolium scaffold: structural features and binding modes
Aim. To assess the structural features of substituents and the role of a thiazolium scaffold in mechanisms of acetylcholinesterase inhibition by thiazolium salts.
Results and discussion. On the basis of activities of model compounds at pH 6.5 and pH 8.0 and the results of molecular docking the binding modes of quaternized derivatives of 5-(2-hydroxyethyl)-4-methylthiazole with different substituents in position 3 and 5 were analyzed. The presence of (N)3-benzyl substituent provides the inhibitor fixation in the catalytic anionic site, whereas acyl fragments of substituents in position 5 are situated in the peripheral anionic site. Logarithms of ІС50 values of the thiazolium inhibitors, except for the compounds containing O-acyl carbocyclic groups, linearly depend on the calculated docking energies in case of a thiazolium, ion as well as a neutral tetrahedral intermediate of the thiazolium ring opening.
Experimental part. Thiazolium salts were synthesized by the known methods. The activity of acetylcholinesterase was studied by Ellman’s method. Molecular docking to the active site of acetylcholinesterase was performed using an AutoDock 4.2 program.
Conclusions. Structural fragments of substituents in positions 3 and 5 of the heterocyclic scaffold provide binding of the inhibitor in the catalytic anionic site and the peripheral anionic site of acetylcholinesterase, respectively. The heterocyclic scaffold can be bound to the enzyme as a thiazolium ion or a neutral tetrahedral
intermediate of the ring opening reaction. -
The reactivity of propyl esters of 2-(benzoylamino)(1-R-2-oxoindoline-3-ylidene) acetic acids
Aim. To study the reactivity of esters of 2-(benzoylamino)(1-R-2-oxoindoline-3-ylidene) acetic acids.
Results and discussion. The reaction rate constants of alkaline hydrolysis of esters of 2-(benzoylamino) (1-R-2-oxoindoline-3-ylidene) acetic acids depend on the structure and the length of the hydrocarbon chain at the heterocyclic nitrogen atom. Introduction of hydrocarbon radicals to the structure of the heterocycle slows down the reaction, while the chain extension accelerates it. The effect of the electronic nature of the substituents on the reactivity of propyl esters was quantitatively assessed by Hammett equation. The data obtained suggest that the values of the reaction parameter ρ are positive in the temperature range studied; it is additionally confirmed by the ВАС2 mechanism of this reaction.
Experimental part. The concentration of NaOH in the solution was determined by potentiometric titration on an EV-74 ionomer using the standard aqueous HCl solution. The reaction kinetics was performed in triplicates, the experiments contained 6-8 measurements (the depth of the change was not less than 80 %). The accuracy of the results obtained was assessed by the methods of mathematical statistics of small samples with statistical significance of 0.95.
Conclusions. The reaction kinetics of alkaline hydrolysis of biologically active propyl esters of 2-(benzoylamino)(1-R-2-oxoindoline-3-ylidene) acetic acids has been studied in a wide temperature range; its ВАС2 mechanism has been proven with formation of a highly symmetrical intermediate. The effect of the substituents at the heterocyclic nitrogen atom on the numerous kinetic and activation parameters of the reaction has been analyzed; isokineticity and synchronicity of the reaction have been proven using independent tests. -
Development and validation of HPLC/UV-procedures for quantification of metronidazole in the blood and urine
Metronidazole belongs to the group of antiprotozoal medicines and widely used for the treatment of infectious diseases; the medicine has a number of side effects manifested by usual symptoms of acute intoxication, especially when interacting with other drugs and alcohol.
Aim. To apply the system of MiLiChrome® A-02 HPLC-analyzer widely used in the Ukrainian laboratories of forensic toxicology for the metronidazole quantitative determination in biological fluids and carry out validation of the procedures developed.
Materials and methods. The sample preparation of blood and urine was carried out by extraction with acetonitrile and 2-propanol followed by separation of the organic layer under the conditions of the aqueous phase saturation with ammonium sulfate. Previously blood and urine were treated with acids. Isolation was carried out in the strong acid, neutral and weak alkaline medium.
Results and discussion. To find the optimal conditions of the sample preparation such validation parameters as specificity/selectivity and recovery were determined. The results of the blank samples analysis were acceptable for all variants of the sample preparation procedures. Recovery values were reproducible for all procedures of analysis studied, but efficacy of metronidazole isolation was variable – from 85% to 97 %. The results of verification of metronidazole stability showed the necessity to carry out all measurements within 12 hours after obtaining the solutions to be analyzed. The results of determination of linearity, accuracy and precision were the evidence
of acceptable systematic and random errors of the HPLC/UV-procedures studied in the variant of the method of calibration curve, method of standard and method of additions.
Conclusions. The set of HPLC/UV-procedures for the metronidazole quantitative determination in blood and urine has been developed. Validation of the procedures developed has been carried out. -
Development and validation of GLC/MS-procedure of doxylamine quantitative determination
Doxylamine is a hypnotic medicine used for treatment of minor sleep disorders and is a frequent cause of poisoning.
Aim. To develop GLC/MS-procedure of doxylamine quantification and carry out step-by-step validation of
the developed procedure in the variants of the method of calibration curve, method of standard and method of additions.
Results. The chromatographic conditions have been chosen for doxylamine determination by the method of GLC with mass-spectrometry detection with temperature program changing during the analysis from 70 °C to 320 °C. Retention time for doxylamine is 14.53 min. To prove the possibility of the proposed procedure application in further analysis its validation has been carried out in the variants of the method of calibration curve, method of standard and method of additions. Such validation parameters as in process stability, linearity, accuracy, precision and limit of determination have been estimated by model solutions.
Experimental part. Conditions of chromatographic analysis: Agilent 6890N/5973N/7683; НР-5MS ∅0.25 mm × 30 m, 0.25 μm; DB-17MS ∅0.25 mm × 30 m, 0.15 μm; columns are connected sequentially through Deans switch; thermostat – 70 CºС (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 procedure of doxylamine quantitative determination by the method of GLC/MS has been developed. Its validation has been carried out and acceptability for application has been shown.
