In the present work, we presented an efficient synthesis and anticancer activity evaluation of some new 3-R-6-(5-arylfuran-2-yl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles. We have shown that the proposed synthetic protocols provided the possibility to design triazolothiadiazoles diversity with a considerable chemical novelty. The structures of target substances were confirmed by using 1H NMR spectroscopy, mass spectrometry and elemental analysis. The synthesized compounds were selected by the National Cancer Institute Developmental Therapeutic Program for the in vitro cell line screening. Among all the substances tested, three compounds exhibited significant cytotoxic activity.
A series of novel 1,3,4-thia(oxa)diazole substituted 2-(2,4-dioxothiazolidine-5-ylidene)-acetamides 3a-c, 4 and 5a-k have been synthesized following the acylation reaction of 2-amino-5-aryl-1,3,4-oxadiazoles, 5-amino-1,3,4-thiadiazole-2-thiol and it’s S-alkylated derivatives with 2-(2,4-dioxothiazolidine-5-ylidene)acetyl chloride in dioxane medium. The functionalization of compounds 3b, 3c, 5d and 5e was carried out on their N3 position under N-alkylation conditions with N-aryl-2-chloroacetamides in DMF/ethanol medium yielded the corresponding 2,4-dioxothiazolidine-3,5-diacetic acid diamides 6a-e and 7a-b. The structures of target compounds were confirmed by using 1H NMR spectroscopy and elemental analysis. The antioxidant activity evaluation in vitro of the synthesized compounds was performed by the method of scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. As a result, the highly active compound 4, namely 2-(2,4-dioxothiazolidin-5-ylidene)-N-(5-mercapto-[1,3,4]thiadiazol-2-yl)acetamide was found to be the most efficient candidate among all compounds with a radical scavenging ability of 88.9%, which was comparable that for ascorbic acid (92.7%). The experimentally calculated IC50 value of 43.1 μM for compound 4 was lower than for ascorbic acid (50.5 μM).
Development of an effective and safe antioxidant compound is still challenging in the last few decades. There has been an increasing interest in the role of reactive oxygen species (ROS) in food, drugs, and even living system. Free radical formation is associated with the normal natural metabolism of aerobic cells. They are inevitably exposed to reactive oxygen species formed as oxygen metabolites. Oxidative stress which is largely characterized by reactive oxygen and nitrogen species is implicated in the development of a number of chronic and degenerative diseases such as atherosclerosis, cancer, cirrhosis, diabetes, wound healing and aging. Free radicals are highly reactive and therefore can attack membrane lipids, generating carbon radicals and peroxy radicals, which cause lipid peroxidation. Therefore, scientists in various disciplines have become more interested in naturally-occurring antioxidants as well as in related synthetic derivatives that could provide active components which prevent or reduce the impact of oxidative stress. Іn order to study the effect of various substituents in the molecules on the nature of thepharmacological activity of thiazolo[4,5-b]pyridin-2-ones, a series of new compounds were synthesized based on the previously obtained 5,7-dimethyl-3Hthiazolo[4,5-b]pyridin-2-one. The high electrophilicity of the N3 position in 5,7-dimethyl-3H-thiazolo[4,5-b]pyridin- 2-one allows to use of its functionalization as a convenient method for obtaining various N3-substituted derivatives to expand the range of thiazolo[4,5-b]pyridines. In particular, an NH center with a mobile hydrogen atom at the N3 position in 5,7-dimethyl-3H-thiazolo[4,5-b]pyridin-2-one allows conducting a synthesis based on 3-substituted derivatives. This conversion was carried out through the stage of obtaining potassium salt. Several chloroacetamides were tested as alkylating agents, which allowed to obtain the corresponding 2-(5,7-dimethyl-2-oxo-thiazolo[4,5-b]pyridin-3-yl)-N-aryl-acetamides (1–6). Methods of quantitative elemental analysis, mass spectrometry, and 1H NMR spectroscopy were used to confirm the structure and individuality of the synthesized substances. Interpretation of the spectra revealed that the signals for protons of all structural units were observed in their characteristic ranges.
Introduction. Nitrogen-based heterocycles are an extremely important class of organic substances widely used in medicinal chemistry, since more than 60% of drugs and more than 85% of biologically active substances described in the literature contain a Nitrogen-containing heterocycle in their structure. The оbjective of thе prеsent study wаs to synthеsize sоme nоvel antiоxidant аgеnts viа a structurаl mоdification оf еarly оbtainеd 3-(5-mercapto-[1,3,4]oxodiazole-2-yl-methyl)-5,7-dimethyl-3H-thiazolo[4,5-b]pyridine-2-one fоr furthеr pharmаcological scrеening in vitrо as antiоxidants.
Results and discussion. For broadening the scope of mercapto substituteds thiazolo[4,5-b]pyridines, we involved 3-(5-mercapto-[1,3,4]oxodiazole-2-yl-methyl)-5,7-dimethyl-3H-thiazolo[4,5-b]pyridine-2-one into cynoethylation reaction taking the advantage of the good leaving hydrogen atom property of the SH-group. It is established that the most optimal conditions for the introduction of the β-cyanoethyl fragment on the base scaffold thiol group consists of the interaction of 3-(5-mercapto-[1,3,4]oxodiazol-2-yl-methyl)-5,7-dimethyl-3H-thiazolo[4,5-b]pyridin-2-one with acrylonitrile in a pyridine-water medium at a ratio of 5:1, this made it possible to obtain the corresponding 3-[5-(5,7-dimethyl-2-oxothiazolo[4,5-b]pyridin-3-ylmethyl)-[1,3,4]oxodiazol-2-ylsulfanyl-propionitrile. Obtained through the mentioned above reaction compound was subjected to hydrolysis leading to 3-(5-hydroxy-7-methyl-2-oxothiazolo[4,5-b]pyridin-3(2H)-yl) propanoic acid formation. For carboxyl group transformation, the corresponding chloranhydride, which belongs to unstable highly reactive reagents was obtained, so its application in further transformations was carried out without isolation by introducing aromatic amines acylation. The above conversion allowed to obtain a number of suitable propionamides. The antioxidant activity of the synthesized compounds was measured in vitro by the method of scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. The present results of аntioxidant activity have shown that the synthesized compounds demonstrated considerable аntioxidant effects. Further optimization of the structure to improve biological activity is currently in progress. Conclusions. A sеries of thiazоlo[4,5-b]pyridinе-2-ones pоssessing аntioxidant аctivities wеre preparеd by the structurаl mоdification of thе cоre heterоcycle. Whеn cоmpared with еxisting аntioxidants, some оur cоmpounds wеre fоund to bе mоre potеnt. Thus the cоre fused heterocyclе mаy be cоnsidered as a prоmising scаffold for аntioxidant drug cаndidates devеlopment.