For many years Toll-like receptor 4 has been associated with the occurrence of sepsis, caused by intrusion of Gram negative bacteria into the human blood. The disease largely occurs in hospitalized patients and its mortality rate is extremely high, therefore it raises a lot of questions about methods and adequacy of the treatment. This is the reason for the high demand for medicinal products with the purpose of treatment or prevention of sepsis. However, despite numerous research in this area, a specific product has not been registered on the market. TLR4 antagonists present high potencial for the development of novel agents against sepsis. These receptors play an important role in the innate immune system and to a lesser extent also affect the adaptive immune response of an individual. TLR4 is well-known and described transmembrane receptor in the TLR group. It typically recognizes molecular patterns associated with pathogens, however, the most important is the recognition of lipopolysaccharide, which is a major component of the cell membrane of Gram negative bacteria. The aim of our master's thesis was to design the synthetic pathway for derivatives of a hit compound with proven antagonism of TLR4, which was discovered at the Faculty of Pharmacy in Ljubljana by virtual screening of the compound library. We examined several synthetic routes and finally discovered the three-stage synthesis of guanidine derivatives. Four final compounds were synthesized and evaluated. We have determined the solubility of compounds in the cell medium, the cytotoxicity in HEK 293 cell line and evaluated the antagonist activity of final compounds on cells which selectively express TLR4. Half maximal inhibitory concentration (IC50) of 27 μM has been determined for one of the final compounds, which shows promising antagonistic activity. However, it would be necessary to synthesize more derivates to obtain additional informations about structure-activity relationship.