ACYCLIC N-nucleosides are prepared by heating under reflux 2-hydrazinocyclopentenothienopyrimidone 1 with aldopentoses in dioxane to give the corresponding acyclic N-nucleosides 2 and 3, which cyclized on stirring at room temperature in acetic anhydride/pyridine mixture to afford the corresponding protected tetra O-acetate C-nucleosides 4 and 5, respectively. De-acetylation of compound 4 and 5 afforded the free acyclic C-nucleosides 6 and 7, respectively. On the other hand, acyclic N-nucleosides 8 and 10 were obtained on treatment of 1 with aldohexoses in the same manner. The protected penta O-acetyl C-nucleosides 11-13 were obtained when stirred compounds 8-10 with acetic anhydride/pyridine mixture at room temperature. De-protection afforded the free acyclic C-nucleosides 14-16, respectively.