Preparing (P1) methyl {4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]pyrimidin-5-yl}methylcarbamate (I), involves cleavage of 2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]-5-[(E)-phenyldiazenyl]pyrimidine-4, 6-diamine by catalytic hydrogenation, and isolation of 2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]-4, 5, 6-pyrimidinetriamine without intermediate formation of salts. Preparing (P1) methyl {4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]pyrimidin-5-yl}methylcarbamate (I), involves : either cleavage of 2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]-5-[(E)-phenyldiazenyl]pyrimidine-4, 6-diamine by catalytic hydrogenation, and isolation of 2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]-4, 5, 6-pyrimidinetriamine without intermediate formation of salts; or reactionof 2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]-4, 5, 6-pyrimidinetriamine with methyl chloroformate or dimethyl dicarbonate to give methyl 4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]-5-pyrimidinylcarbamate via a pyridine-free reaction route. Independent claims are included for the following : (1) purifying methyl {4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]pyrimidin-5-yl}methylcarbamate, involving dissolving crude methyl {4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]pyrimidin-5-yl}methylcarbamate in dimethyl sulfoxide; isolating the resulting methyl {4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]pyrimidin-5-yl}methylcarbamate sulfinyldimethane; and removing the dimethyl sulfoxide by boiling in a solvent; (2) new methyl {4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]pyrimidin-5-yl}methylcarbamate sulfinyldimethane (II); and (3) methyl {4, 6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3, 4-b]pyridin-3-yl]pyrimidin-5-yl}methylcarbamate is prepared by the process (P1). ACTIVITY : Cardiovascular-Gen.; Cardiant; Antianginal; Vasotropic; Antiarrhythmic; Thrombolytic; Cerebroprotective; Thrombolytic; Antiarteriosclerotic; Antiasthmatic; Cytostatic; Endocrine-Gen.; Osteopathic; Ophthalmological; Hypotensive; Respiratory-Gen.; Uropathic. No biological data given. MECHANISM OF ACTION : Soluble guanylate cyclase stimulator.