| abstract |
A process for the preparation of 9-substituted guanine derivatives of general formula (I), in which R is C1-C4-alkyl optionally substituted with one or more hydroxy groups, or R is ( alpha ), benzyl, ribosyl, 2'-deoxyribosyl or (CH2)n-OR<1> where n is 1 or 2, and R<1> is CH2CH2OH or ( beta ) or salts thereof, in which a 1-substituted 5-(thiocarbamoyl)amino-1H-imidazole-4-carboxamide of general formula (III), where R has the same meaning as in formula (I), is cyclized: a) by treatment with a heavy metal salt of the group of Cu-, Ag-, Pb- and Hg-salts in an aqueous alkaline medium containing at least four equivalents of OH<->ions at a temperature from about 0 DEG C to the reflux temperature, or b) by treatment with a peroxy compound in an aqueous alkaline medium at a temperature of about 0-30 DEG C, whereafter (I) is isolated by treatment with acid and, if desired, is converted into a salt. The invention further comprises intermediates for use in the preparation of the above-mentioned compounds. |