The search for new and efficient pharmaceuticals is a constant struggle for medicinal chemists. New substances are needed in order to treat different pathologies affecting the health of humans and animals, and these new compounds should be safe, effective and have the fewest side effects possible. Some functional groups are known for having biological activity; in this matter, the nitro group (NO2) is an efficient scaffold when synthesizing new bioactive molecules. Nitro compounds display a wide spectrum of activities that include antineoplastic, antibiotic, antihypertensive, antiparasitic, tranquilizers and even herbicides, among many others. Most nitro molecules exhibit antimicrobial activity, and several of the compounds mentioned in this review may be further studied as lead compounds for the treatment of H. pylori, P. aeruginosa, M. tuberculosis and S. mutans infections, among others. The NO2 moiety triggers redox reactions within cells causing toxicity and the posterior death of microorganisms, not only bacteria but also multicellular organisms such as parasites. The same effect may be present in humans as well, so the nitro groups can be considered both a pharmacophore and a toxicophore at the same time. The role of the nitro group itself also has a deep effect on the polarity and electronic properties of the resulting molecules, and hence favors interactions with some amino acids in proteins. For these reasons, it is fundamental to analyze the recently synthesized nitro molecules that show any potential activity in order to develop new pharmacological treatments that enhance human health.

Abstract:: The heterocycle ring tetrazole is an important moiety relevant to medicinal chemistry since it is present in some drugs with clinical importance. Its primary biological activity is being a bioisosteric analogue of the carboxylic acid and cisamide groups. Its metabolic stability and other physicochemical properties make it an attractive structure for designing and synthesizing new pharmaceuticals. The biological activity of tetrazoles is quite extensive and includes antiviral, antibacterial, anticancer, antifungal, and antioxidant properties; all of them are discussed in this review. The most effective way to obtain tetrazoles is by azide derivatives, either in the starting materials like the cycloaddition [3 + 2] of organic azides and nitriles or by preparing a reactive imidoyl azide intermediate. The nucleophilic behavior of the azide group is discussed when the raw materials include isocyanides. Some other methods include alternative synthetic routes like thermoslysis. This review also highlights some of the developments regarding the use of different heterogeneous catalysts to synthesize different tetrazole derivatives.

Background: Fluoroquinolones are widely prescribed synthetic antimicrobial agents. Quinolones act by converting their targets, gyrase and topoisomerase IV, into toxic enzymes that fragment the bacterial chromosome; the irreversible DNA damage eventually causes the killing of bacteria. Thorough knowledge of the structure-activity relationship of quinolones is essential for the development of new drugs with improved activity against resistant strains. Methods: The compounds were screened for their antibacterial activity against 4 representing strains using the Kirby-Bauer disk diffusion method. Minimal inhibitory concentration (MIC) was determined by measuring the diameter of the inhibition zone using concentrations between 250 and 0.004 μg/mL. Results: MIC of derivatives 2, 3, and 4 showed potent antimicrobial activity against gram-positive and gram-negative bacteria. The effective concentrations were 0.860 μg/mL or lower. MIC for compounds 5-11 were between 120 and 515 μg/mL against Escherichia coli and Staphylococcus aureus, and substituted hydrazinoquinolones 7-10 showed poor antibacterial activity against gram-positive and gram-negative bacteria compared with other quinolones. Conclusion: Compounds obtained by modifications on C-7 of norfloxacin with the acetylated piperazinyl, halogen atoms, and substituted hydrazinyl showed good in vitro activity - some even better than the original compound.

Nowadays, the pharmaceutical industry faces the challenge of innovating and increasing the productivity of new medicines due to the increasing multidrug resistance among bacteria, viruses and fungi. The main objective of the present study is connected quinolone and triazole molecules to enhance and broad antibacterial spectrum as well as to have multiple mechanisms of action. Preparation of 4‐substituted‐1H‐1,2,3‐triazol‐1‐yl in C‐7 of 6‐fluoro‐ and 6,8‐difluoro‐quinolone ring is showed. The synthesis involved the preparation of intermediate ethyl 7‐azide‐1‐ethyl‐fluoroquinolone‐3‐carboxylate, followed by copper(I)‐catalyzed azide‐alkyne cycloaddition to give 13 derivatives. The cycloaddition was carried out by two different methods, where it was observed that the microwave radiation was the best reaction condition, obtaining a range of yields of 47–93%, at 140 °C, 125Wmax for 10 minutes. Therefore, this methodology provided an easy pathway to synthesize a library of fluoroquinolones coupled to 1,2,3‐triazole, still unexplored.

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