# Synthesis and Biological Activity of 1,3,4-Oxadiazoles Used in Medicine and Agriculture
###### Abstract  
Biologically active compounds play a key role in the fight against diseases affecting both human and animal living organisms, as well as plants. Finding out about new molecules with a potential biological effect, not yet described in the literature, is one of the most important aspects in the development of medicine and agriculture. Compounds showing desirable biological activity include heterocyclic moieties such as 1,3,4-oxadiazoles. The oxadiazole molecule is composed of two nitrogen atoms and one oxygen atom, forming a five-membered heterocyclic ring. Structures of this type have been successfully used in the treatment of various diseases in humans and animals, and play an important role in modern agriculture. It has been proven that many oxadiazole derivatives exhibit antibacterial, antiviral, blood pressure lowering, antifungal, antineoplastic, anticancer, antioxidant, anti-inflammatory and analgesic properties. In addition, compounds based on 1,3,4-oxadiazole can act as plant protection agents due to their herbicidal, insecticidal and fungicidal activity. Due to the constantly growing interest in heterocyclic systems of this nature, new methods of obtaining complex structures containing oxadiazole rings are sought. This article discusses various methods of synthesis of 1,3,4-oxadiazole derivatives exhibiting biological activity. Based on these techniques, these compounds could be used in the future in medicine and agriculture.  
1,3,4-oxadiazoles; medicine; agriculture; biological activity; synthesis +
Footnote †: journal: Applied Physics Letters  
_Applied_  
as pneumocytosis [6]. The irrational use of antimicrobials in the clinical and veterinary sectors has led to the selection, spread, and evolution of multidrug-resistant microorganisms. To overcome this problem, combinational therapies that combine several antimicrobial substances are widely used in the pharmaceutical industry. However, high toxicity is often observed, and drug-drug interactions cannot always be effectively predicted. Therefore, the development and synthesis of polyactive compounds which selectively and simultaneously target several pathogens can help in the fight against antimicrobial resistance. A literature study revealed that complex 1,3,4-oxadiazole derivatives are valuable compounds in this respect. These molecules are widely used in the production of many biopharmaceutical substances, showing a wide range of biological activities [7].  
Oxadaizoles belong to the group of heterocyclic compounds which contains one oxygen and two nitrogen atoms, forming a five-membered heterocyclic ring. The oxadiazole molecule is derived from furan, where two carbon atoms are replaced by nitrogen atoms of the pyridine type. Oxadaazole molecules have many properties that are used in various industries. These compounds exhibit a wide spectrum of biological activity, which makes it possible to apply them in medicine and pharmacology as active agents, e.g., with anti-inflammatory and analgesic [8], antimicrobial [9], antiviral [10], antifungal [11], antitumor [12] and blood pressure lowering properties [13]. The antimicrobial properties of 1,3,4-oxadaizoles were the subject of a recent review [14]. Due to the potential biological activity of this type of compound, they are also used in agriculture as herbicides, insecticides and plant protection agents against diseases caused by bacteria, viruses and fungi. The oxadiazole moieties also have valuable optical properties. The 1,2-diazole fragment present in the molecule acts as an electron withdrawing group, so it is widely used in various types of conducting systems [15]. It is therefore possible to increase the quantum yield of fluorescence and improve the stability of the molecule. For this reason, oxadaizole derivatives are used as organic light emitting diodes, laser dyes, optical brighteners and scintillators [15; 16; 17]. These molecules can be also found in materials such as thermal insulation polymers (Figure 1) [18].