Vol. 18 No. 4(72) (2020)
The synthesis, transformations and biological activity of thieno[2,3-d]pyrimidine derivatives with the carboxylic groups as the substituents in the pyrimidine ring
Aim. To reveal the prospects of the search of novel medicinal substances based on the studies of the derivatives of thieno[2,3-d]pyrimidine with the carboxylic groups as the substituents in the pyrimidine ring using the analysis of the published literature data.
Results and discussion. The study has shown a wider range of the pharmacological activity of thieno[2,3-d]pyrimidine-2-carboxylic acid derivatives compared to thieno[2,3-d]pyrimidine-4-carboxylic acids, as well as their availability, despite the fact that the number of preparative methods for the synthesis of these substances is rather limited. The most popular method is cyclization of 2-aminothiophene-3-carboxylic acids with ethyl cyanoformate. On the other hand, thieno[2,3-d]pyrimidine-4-carboxylic acid derivatives are presented in even fewer studies and are poorly studied; many of them are difficult to be synthesized and practically are not found in the pharmacological patent literature.
Conclusions. The literature data analysis has revealed the small number of efficient synthetic methods suitable for preparation of thieno[2,3-d]pyrimidines with the carboxylic groups as the substituents in the pyrimidine ring, as well as their low availability for the pharmacological studies. It is also noteworthy that the derivatives of thieno[2,3-d]pyrimidine-4-carboxylic acids are even less studied than the related compounds of thieno[2,3-d]pyrimidine-2-carboxylic acid series, and therefore, more attention should be paid to them as the objects for experimental chemistry and pharmacology.
The synthesis of cis- and trans-3-(4-hydroxyphenyl)cyclobutanecarboxylic acids and the study of their derivatives as GPR-40 receptor ligands
Aim. To synthesize cis- and trans-isomers of 3-(4-hydroxyphenyl)cyclobutanecarboxylic acid and evaluate the biological activity of their derivatives against GPR-40.
Results and discussion. Cis- and trans-isomers of 3-(4-hydroxyphenyl)cyclobutanecarboxylic acid were synthesized. The derivatives of this compound were tested as GPR-40 agonists and exhibited the micromolar activity.
Experimental part. The methyl ester of 3-(4-hydroxyphenyl)cyclobutanecarboxylic acid was obtained as a mixture of cis/trans-isomers in 3 steps starting from a commercially available 3-oxocyclobutanecarboxylic acid. Further transformation of this compound into isomerically pure 3-(4-hydroxyphenyl)cyclobutanecarboxylic acids was achieved in five steps based on the chromatographic separation of diastereomeric amide derivatives. New GPR-40 ligands were obtained by O-alkylation of a phenolic oxygen atom of the corresponding carboxylic acid methyl ester. The biological activity of the agonists synthesized was studied using a fluorometric bioassay and the engineered Chinese hamster ovary (CHO) stable cell line expressing the human GPR-40.
Conclusions. An effective synthetic approach to 3-(4-hydroxyphenyl)cyclobutanecarboxylic acid allowing to isolate two single cis/trans-stereoisomers of this compound has been developed. In order to demonstrate the possibility for the bioisosteric replacement of the ethylene moiety in the structures of free fatty acid receptor (FFAR) agonists by the cyclobutane ring, four new GPR-40 ligands possessing the micromolar activity have been synthesized.
Acylation of indolyl subsituted β-ketonitriles. The way to new indolo[2,3-c]pyrilium and β-carboline derivatives
Aim. To synthesize 4-cyanoindolo[2,3-c]pyrilium salts and examine their reactivity towards N-nucleophiles.
Results and discussion. The acylation reaction of 2-(indolyl-3)-2-aroylacetonitriles under acid catalysis conditions was studied. 4-Cyanoindolo[2,3-c]pyrillium borofluorides were obtained, and ketonitrile enolacylates were isolated as by-products of the reaction. Treatment of the 4-cyanoindolo[2,3-c]pyrilium salts with ammonia led to 4-cyano-β-carbolines while the interaction of the salts with hydrazine hydrate resulted in formation of pyrazolo[3’,4’:5,6]pyrido[3,4‑b]indoles – derivatives of a new heterocyclic system. The latter are formed via recyclization involving the pyran ring and the cyano group.
Experimental part. Upon the treatment of 2-(indolyl-3)-2-aroylacetonitriles with acetic anhydride/tetrafluoroboric acid mixture, the acylation of the indole fragment in position 2 was followed by cyclization, resulting in formation of 4-сyanoindolo[2,3-c]pyrilium salts. The reactivity of the pyrylium salts was studied on the examples of their interaction with N-nucleophiles – ammonia and hydrazine hydrate. The structure of the compounds synthesized was confirmed by 1H NMR, IR spectroscopy and elemental analysis.
Conclusions. It has been found that moderate yields of 4-сyanoindolo[2,3-c]pyrilium salts are the result of competing acylation of the hydroxyl group of enol ketonitrile, which blocks the pyran ring formation. Recylization of the salts with ammonia leads to 4-cyano-β-carbolines. Transformation of the pyran ring with hydrazine hydrate proceeds with the participation of the cyano group as a tandem reaction with formation of pyrazolo[3’,4’:5,6]pyrido[3,4-b]indoles.
The synthesis and the study of the antitumor activity of 3-R-6-(4-methoxyphenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine hydrobromides
Aim. To synthesize and study the antitumor activity of 3-R-6-(4-methoxyphenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine derivatives.
Results and discussion. To determine the antitumor activity of 3-R-6-(4-methoxyphenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine hydrobromides, the in vitro study was conducted on 60 lines of cancer cells (leukemia, non-small cell lung cancer, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, prostate cancer and breast cancer) according to the standard procedure of the mitotic activity assessment of new potential bioactive compounds by the fluorescent coloring method (sulforhodamine B as a dye). It was performed in the US National Сancer Institute within the Development Therapeutic Program. It has been found that derivatives of 3-R-6-(4-methoxyphenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine exhibit the antineoplastic activity against a wide range of cancer cells lines and are promising core structures for creating new effective anticancer agents.
Experimental part. 3-R-6-(4-methoxyphenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine hydrobromides were synthesized by the interaction of 4-amino-5-R-4H-1,2,4-triazole-3-thiols with 4-methoxyphenacyl bromide in ethyl acetate. The 1Н NMR spectra were recorded on a Bruker VXR-300 spectrometer (Germany) with the working frequency of 299.945 MHz.
Conclusions. A series of 3-R-6-(4-methoxyphenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine hydrobromides has been synthesized. The anticancer activity of the compounds obtained has been studied in the National Cancer Institute on 60 lines of tumor cells. Compounds that exhibit high levels of the antitumor activity have been found. It has been shown that the replacement of 3-H in compound 3a with ethyl or pentyl radicals leads to increase in the antitumor activity against MDA-MB-468 breast cancer cells.
Bromination of quinolin-4(1H)-ones as an efficient strategy for the development of new antibacterial agents
Aim. To study the reactivity of 2-methylquinolin-4(1H)-ones in the bromination reaction in order to develop target-oriented methods for the synthesis of compounds that can affect the Quorum sensing processes of various bacterial communities.
Results and discussion. Features of the reactivity of 2-methylquinoline-4(1H)-ones in the bromination reaction using two halogenating reagents – molecular bromine and N-bromosuccinimide (NBS) have been studied. It has been shown that in both cases the direction of halogenation depends on the presence and nature of the substituent in position C(3) of the heterocycle. It has been found that variations in reagents, solvents, and catalysts did not lead to changes in the qualitative composition of the reaction products and only slightly affected their yields.
Experimental part. The synthesis of bromo derivatives of quinoline-4(1H)-ones was carried out by acting on the initial compounds of a molecular bromine or NBS in glacial acetic acid or chloroform, respectively, in the presence of catalytic amounts of benzoyl peroxide or without it. The structure of the compounds synthesized was proven by the data of 1H NMR spectroscopy and elemental analysis.
Conclusions. The features of the bromination reaction in the series of 3-substituted 2-methylquinolin-4(1H)-ones have been studied. It has been found that depending on the nature of the substituent in position C(3) of quinolone, bromination occurs on the methyl group of position C(2), or on positions C(3) and C(6) of the heterocycle. In the case of 3-benzyl-2-methylquinolin-4(1H)-one, bromination takes place on the methyl group of position C(2) of quinolone to form 3-benzyl-2-(bromomethyl)quinolin-4(1H)-one, which can be used for developing a new class of drugs designed to affect the virulence factors of microorganisms. The reactivity of 3-benzyl-2-(bromomethyl)-quinolin-4(1H)-one has been studied on the example of n-hexylamine alkylation.
The Pharmacophore Model for the Antistaphylococcal Activity Screening Among Thiazolidinone-Related Structures
Aim. To develop a pharmacophore model suitable for the antistaphylococcal activity screening among thiazolidinone, thiopyrano[2,3-d]thiazole and thiazolo[4,5-b]pyridine derivatives.
Results and discussion. The best pharmacophore model in the series of models developed has a planar structure and consists of an aromatic ring (or cycle with π-bonds), a hydrophobic region, a projection of a hydrogen bond donor and two projections of a hydrogen bond acceptor. Its classification accuracy is 72.4 %. The diameter line of the model is formed by the projection of the hydrogen bond donor and the projection of the hydrogen bond acceptor, and its length is 8.05 Å. The analysis of conformations of active compounds consistent with the pharmacophore mode revealed two different ways of spatial arrangement of active molecules, in which the conditions of the pharmacophore model are fully met.
Experimental part. The antistaphylococcal activity was determined by the agar diffusion method against methicillin-resistant strain of Staphylococcus aureus (MRSA) and evaluated by measuring the diameter of the microbial growth inhibition zone. The plates were incubated for 24 h at 37 °C. Compounds with the growth inhibition diameter of more than 7.5 mm were considered to be active. Computer processing of the results of the microbiological experiment and modeling of the probable pharmacophore were performed in the MOE software environment version 2007.09. The geometry of the compounds was optimized by molecular mechanics using the MMFF94x force field. Accuracy of classification was used as the main quality criterion of the pharmacophore model.
Conclusions. The pharmacophore model developed can be used for virtual screening of the antistaphylococcal activity for the compounds similar to the training sample. When applying it to the in-home database of compounds the enrichment factor is EF = 2.05.
The thermodynamic study of morpholinium 2-((4-(2-methoxyphenyl)-5-(pyridinyl)-4H-1,2,4-triazol-3-yl)thio)acetate and its technological impurities in hydrophilic chromatography
Aim. To study the dependence of the retention of morpholinium 2-((4-(2-methoxyphenyl)-5-(pyridinyl)-4H-1,2,4-triazol-3-yl)thio)acetate and its technological impurities on temperature, as well as determine the thermodynamic characteristics of the transfer from the mobile phase to the stationary phase using hydrophilic chromatography.
Results and discussion. The retention factors depending on the absolute temperature were determined in order to study the thermodynamic parameters of the transfer of analytes from the mobile phase to the stationary one. Based on the van ‘t Hoff equation a curve of lnk dependence on 1/T was constructed. The least squares method was used to create the linear dependence equation. The standard molar enthalpies, as well as the conditional standard entropy of the transfer from the mobile to the stationary phase of the test substances, namely morpholinium 2-((4-(2-methoxyphenyl)-5-(pyridinyl)-4H-1,2,4-triazol-3-yl)thio)acetate, pyridine-4-carbohydrazide, 2-isonicotinoyl-N-(2-methoxyphenyl)hydrazine-1-carbothioamide and 4-(2-methoxyphenyl)-5-(pyridinyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione were calculated. The negative enthalpy of the transfer for all substances shows that the substances are adsorbed on the surface of a silica gel with the release of heat. Therefore, the process of transition of a substance from the mobile phase to the stationary one prevails over the reverse process.
Experimental part. The Agilent 1260 Infinity liquid chromatography system consisting of a degasser, binary pump, autosampler, column thermostat, diode array detector was used for our experiments.
Conclusions. It has been found that all the compounds studied have a negative value of the transfer enthalpy, and it indicates the predominant transition of these analytes from the mobile phase to the stationary one. Conditional standard entropies of the analyte transfer from the mobile phase to the stationary phase have been calculated, and it has been proven that they significantly affect the transfer process.
Aim. To study the qualitative composition and the quantitative content of fatty acids in Pimpinella anisum herb.
Results and discussion. As a result of the study, 11 fatty acids were found in the herb of Pimpinella anisum. Of them, saturated fatty acids are represented by 9 compounds, while unsaturated ones by 2 compounds. Among saturated fatty acids, palmitic acid (11.20 mg/g) predominates; unsaturated α-linolenic and linoleic acids are contained in approximately equal amounts – 5.23 and 4.99 mg/g, respectively.
Experimental part. Pimpinella anisum herb grown and harvested at the flowering stage in the summer of 2019 in the Kharkiv region, Ukraine, was used for the analysis. Chromatographic separation was performed on an Agilent 6890N/5973inert gas chromato-mass spectrometric system (Agilent Technologies, USA). The capillary column was HP-5ms (30 m × 0.25 mm × 0.25 mm, Agilent Technologies, USA). Detection was performed in a SCAN mode in the m/z range of 38-400. Fatty acid methyl esters were identified using the NIST 02 mass spectrum library. The quantitative analysis was performed by adding the internal standard solution to the test samples.
Conclusions. The qualitative composition and the quantitative content of fatty acids in the herb of Pimpinella anisum have been determined by gas chromatography-mass spectrometry. The presence of 11 fatty acids has been determined. The data obtained will be useful for creating herbal products based on Pimpinella anisum.