Synthesis of Novel Pyridine Bearing Biologically Active Imidiazolyl, Pyrazolyl, Oxa/thiadiazolyl and Urea Derivatives as Promising Anticancer Agents

Background: A novel series of pyridine containing 1,3,4-oxa/thiadiazol derivatives 4a,b, pyrazole derivatives 5-7, thiazole derivatives 9a,b and 17a-c, urea derivatives 12a-c, imidiazole derivative 16, imidazo[1,2-a]pyridine derivatives 18a, b, tetrazole 19, pyrane 20 and pyridine derivatives 21 has been synthesized. Objective: This research aims to synthesize 6-(Trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl] amino} nicotinohydrazide 2 and 6-(trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl]amino} pyridin-3-carboaldhyde 15 as key intermediate for the synthesis of novel pyridine derivatives bearing different heterocyclic rings in order to study the additive effect of this ring toward tumor cell lines. Methods: 6-(Trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl]amino} nicotinohydrazide 2 was synthesized in a series of synthetic steps and was used as key intermediate for the synthesis of compounds 3-(1,3,4- oxa/thiadiazol-2-yl)-6-(trifluoromethyl)-N-(3- trifluoromethyl) phenyl) pyridin-2-amine 4a,b, (3,5-dimethyl- 1H-pyrazol-1-yl derivatives) [6-(trifluoromethyl)-2-{[3- trifluoromethyl) phenyl] amino} pyridin-3- yl]methanone 5a,b, 6-8, 9a,b and 12a-c. Also, 6-(trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl]amino} pyridin-3-carboaldhyde (15) was used as a key intermediate for the synthesis of novel series of pyridine derivatives with different heterocyclic ring (16-21). Results: Structures of the newly synthesized compounds were established by elemental analysis and spectral data. All the synthesized compounds were screened for their in vitro anticancer activity against liver cancer (HepG2), human colon cancer (HT-29) and human breast adenocarcinoma cell lines (MCF-7). Conclusion: All the synthesized compounds were investigated for their in vitro antitumor activity. Compounds 4b, 9a,b and 19 showed higher antitumor activity than the doxorubicin. Interestingly, pyridine with pfluorophenyl urea 12a demonstrated the most potent antitumor activity. The activity of these compounds is strongly dependent on the basic skeleton of the molecules and the nature of the heterocyclic ring attached to the pyridine moiety.