FIELD: organic chemistry, nucleosides. SUBSTANCE: invention proposes compounds of the formula: 
where X means H, NR-R1, SR, OR or halogen; Z means H, OR2 or NR-R1; R, R1 and R2 mean H, C1-C4-alkyl or aryl and their pharmaceutically acceptable salts. Invention proposes also the use of these compounds as antiviral and antitumor agents, pharmcomposition based on thereof and methods of synthesis of the parent and intermedium compounds.. EFFECT: improved method of synthesis. 16 cl, 2 tbl, 27 ex
