In this dissertation, the synthesis of new stilbene derivatives containing in their structures het-erocyclic nuclei of furan, thiophene, triazole, thiazole and pyranone was designed, and success-fully carried out using the Wittig reaction, the McMurry reaction and the Buchwald-Hartwig amination reaction. Photochemical illumination was performed on the synthesized conjugated derivatives in order to obtain new electrocyclization photoproducts. New derivatives were tested for their biological activity as potential cholinesterase enzyme inhibitors with anti-in-flammatory and antioxidant activity or as cholinesterase reactivators. Known stilbene deriva-tive with pronounced biological activity such as resveratrol, pterostilbene and others served as model compounds. Heterostilbene molecules contain heterocyclic nuclei that are crucial in the metabolism of living cells, and are of exceptional importance for the development of agents against neurodegenerative diseases, in which enzymes cholinesterases play a leading role. As different heterostilbene derivatives are already used in the production of nonlinear optical ma-terials (NLO), photochemical reactivity and the formation of photocyclization products were also investigated in detail, as well as the photophysical behavior of the new heterostilbenes. The synthesis was carried out with a conventional approach, but also with a modern synthetic approach, using flow-chemistry and flow-photochemistry, in order to increase the productivity and economy of the process. On the basis of computer methods, the potential binding of new structures to the active sites of enzyme cholinesterases, as well as the electronic structure of the molecules, were examined. Among the large number of new structures, a certain number of molecules stood out with very good inhibitory activity towards enzyme cholinesterases, but also antioxidant and anti-inflammatory activity. Heterostilbene derivatives with the best pre-liminary results provide guidelines for further research in finding new enzyme cholinesterase inhibitors or reactivators with additional antioxidant and anti-inflammatory effects or suitable photophysical characteristics. Biological tests were carried out in cooperation with the University of Mostar and the company Selvita, while computational study, photophysics and spectroscopic measurements were carried out in cooperation with the Ruđer Bošković Institute. Tests on the complexation of compounds with biometals, and interpretations of the photocatalytic oxygenation were carried out in coop-eration with the Pannonia University in Veszprém. Biological tests of cholinesterase reactiva-tion were investigated in collaboration with colleagues from the Institute for Medical Research and Occupational Medicine. Computational study on the photochemistry and photophysics of excited molecules in correlation with experimental results were carried out in cooperation with Yale University. Analyzes of compounds and synthesis of compounds using flow-reactors were carried out in collaboration with colleagues from the Faculty of Chemical Engineering and Technology at University of Zagreb and from the Pliva company.