The search for new drugs in the group of xanthine derivatives. XXXVIII - 1,3-dimethyl-8-alkyl-6H,7H,10H-(1,2,4-)-triazepino(4,3-f)purine-2,4-(1H,3H)-diones and their derivatives.

Condensation of 1-(8'-chlorotheophyllinyl-7')-alkan-3-ones with hydrazine hydrate gave 8-alkyl derivatives of the new heterocyclic ring system: 1,3-dimethyl-6H,7H,10H-(1,2,4)-triazepino [4,3-f] purine-2,4-(1H,3H)-dione (I, II). 10-Acyl (III - VI) and 10-beta-cyanoethyl (VII, VIII) derivatives of compounds (I) and (II) were easy obtained in good yield. With p-nitrophenyl- and isonicotinoylhydrazines only the corresponding hydrazones of 1-(theophyllinyl-7')-alkan-3-ones (IX, X) were formed. In the attempt to obtain 10-aryl, hydroxyalkyl or acyl derivatives of the new tricyclic ring system by the reaction of 1-(8'-chlorotheophyllinyl-7')-butan-3-one with phenyl-, beta-hydroxyethyl- or acetylhydrazines only decomposition of the ketones to 8-chlorotheophylline and vinylketones was observed. The structures of the new compounds were confirmed by U.V. and N.M.R. spectroscopy and partly by mass spectrometry.