Derivatives of purine, process for their preparation and a pharmaceutical preparation

Antivirally active compounds of formula (I), wherein R1 is hydrogen, hydroxy, mercapto or amino; R2 is hydrogen, hydroxy, fluoro, chloro or amino; R3 and R4 are independently selected from (II), (III), amino, hydroxy or an ether or ester residue thereof, or R3 together with R4 is (IV), wherein M is hydrogen or a pharmaceutically acceptable counterion; and n is 1 or 2; with the proviso that, when R2 is amino and R3 and R4 are hydroxy, R1 is not hydroxy and in addition, when n=1, R1 is not hydrogen, and pharmaceutically acceptable salts thereof; processes for preparation of said compounds, a pharmaceutical composition comprising said compounds, methods for treatments of virus infections as well as use of compounds of formula (I) without the proviso for the manufacture of a medicament for treatment of AIDS. (I) (II) (III) (IV)