Abstract: The present invention provides desazapurine-nucleoside derivatives of the general formula: wherein X is a nitrogen atom or a methine radical, W is a nitrogen atom or a C—R4 radical, R1, R2, R3 and R4, which can be the same or different, are hydrogen or halogen atoms, hydroxyl or mercapto groups, lower alkyl, lower alkylthio, lower alkoxy, aralkyl, aralkoxy or aryloxy radicals or amino groups optionally substituted once or twice, R5 is a hydrogen atom or a hydroxyl group, R6 and R7 are each hydrogen atoms or one of them is a halogen atom or a cyano or azido group or an amino group optionally substituted once or twice, whereby one of R6 and R7 can also be a hydroxyl group when X is a methine radical and, in addition, R5 and R7 can together also represent a further valency bond between C-2′ and C-3′ and Y is a hydrogen atom or a mono-, di- or tri-phosphate group.