In response to the AIDS epidemic, the discovery of antiviral agents has been focused on the synthesis of nucleoside analogues. The basis moiety of these pyrimidine nucleosides were thieno and thiano[3,2-d]pyrimidine-2,4-dione possibly substituted on 7 position by methyl or aryl groups, 6,7-dihydrothieno[3,2-d]pyrimidin-4-one, bicyclic heterocycles including an uracil moiety. The first part of organic chemistry work has provided cyclic and acyclic N-nucleosides after adaptation of Vorbrüggen and Niedballa method. The carbohydrate fraction of these nucleosides included either a cyclic sugar yielding uridine, ARA U and IDU analogues or an hydroxylated chain that allowed access to aciclovir, ganciclovir and EBPU analogues. The second part has been devoted to functional arrangements beta-D-ribonucleoside respectively on carbohydrate and aglycon moieties carrying into reduction (synthesis of an unsaturated dideoxynucleoside, a d4T analogue) and amination reactions (cytidine analogue). Several compounds were tested against HIV1 in CEM cl 13 cell cultures, but none of them exhibited significant activity against this virus.