Purine derivatives and use thereof in therapy

Abstract From the Canadian patent

Antivirally active compounds of the formula (see fig I), wherein:, R1 is hydrogen, hydroxy mercapto or amino;, R2 is hydrogen, hydroxy fluoro, chloro or amino;, R3 and R4 are independently selected from (see fig II), amino, hydroxy, or an ether or ester residue thereof or, R3 together with R4 is (see fig III) 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 treatment …