!ntroduction Analogues ofnucleic acid components belong to the most successful classes oftherapeutics. Extensive modifications ofnucreobases, nucreosides and nucleotides led to the discovery ofa huge group of compounds with remarkable biological activity. The most important are perhaps the effects on various severe diseases such as cancer, leukemia or viral infectrons. The essential aim ofthis Thesis was the preparation ofbiologically active compounds related to the nucleic acid components. Since the carbocyclic anďogues ofnucleosides have been a long-time interest of our group, the first part of this work was devoted to the development of practical synthetic routes towards their new derivatives and to the synthesis of the novel analogues for further biological activity screening. However, the preliminary biological tests of the prepared compounds uncovered very promising lead to the compretely different field than it was expected. During the primer studies, I synthesized several 5,6-disubstituted uracils, initially prepared just as moder compounds for development of nover synthetic approaches towards carbocyclic nucleosides, that showed to posses outstanding inhibitory activity against thymidine phosphorylase. Therefore, the development of novel derivatives based on these findings was estabrished as a new..
