[C:1]([C:3]1[CH:4]=[CH:5][C:6]([O:19][CH2:20][CH2:21][CH3:22])=[C:7]([C:9]2[N:17]=[C:16]3[C:12](=[N:13][N:14]=[N:15]3)[C:11](=[O:18])[N:10]=2)[CH:8]=1)#[N:2].S(=O)(=O)(O)[OH:24]>O>[C:1]([C:3]1[CH:4]=[CH:5][C:6]([O:19][CH2:20][CH2:21][CH3:22])=[C:7]([C:9]2[N:17]=[C:16]3[C:12](=[N:13][N:14]=[N:15]3)[C:11](=[O:18])[N:10]=2)[CH:8]=1)(=[O:24])[NH2:2]2-(5-Cyano-2-propoxyphenyl)-8-azapurin-6-one (2.0 g; prepared as described in Example 6) was carefully added with stirring to concentrated sulphuric acid (20 ml) during 10 minutes. The resulting solution was allowed to stand at room temperature for 3 hours, and then it was poured into iced water (100 ml) and the mixture was allowed to stand for 2 hours. The resulting solid was then filtered off and dissolved in aqueous sodium carbonate solution (2 N; 50 ml). This solution was treated with charcoal, filtered, and acidified by the addition of concentrated hydrochloric acid, and the resulting white solid was recrystallised from dimethylformamide. The recrystallised solid was dissolved in aqueous sodium carbonate solution (2 N; 50 ml) and the solution was acidified by the addition of concentrated hydrochloric acid and the resulting solid was filtered off to give 2-(5-carbamoyl-2-propoxyphenyl)-8-azapurin-6-one (0.9 g), m.p. 273°-275° C. (with decomposition).
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