Syntheses of Some Tricyclic Heterocycles from 5, 6-Diamino-1, 3-dimethyluracil

抄録

5-Amino-6-mercapto-1, 3-dimethyluracil (2) was prepared by the treatment of 5, 6-diamino-1, 3-dimethyluracil (1) with liquid H₂S and pyridine in a sealed steel tube at 60°C for 20 h. Thiazolo[5, 4-d]pyrimidinediones 3a, b were obtained from 2 by cyclization with HCO₂H and AcOH.Under stringent conditions, however, 1 was converted into the 5, 9-dihydrodipyrimido[4, 5-b : 5', 4'-e][1, 4]thiazine derivtive 4a.The structure of 4a was confirmed by spectral (nuclear magnetic resonance and mass spectra) data and by comparison with a sample which was prepared from 2 and 5-hydroxy-1, 3-dimethyluracil.Benzylation of 4a gave 1, 3, 7, 9-tetramethyl-5-benzyl (or p-bromobenzyl)-5, 9-dihydrodipyrimido[4, 5-b : 5', 4'-e][1, 4]thiazine-2, 4, 6, 8-(1H, 3H, 7H)-tetrone (4b, c) and 1, 3, 7, 9-tetramethyl-5-benzyl (or p-bromobenzyl)-5, 9-dihydropyrrolo[3, 2-d : 4, 5-d']dipyrimidine-2, 4, 6, 8-(1H, 3H, 7H)-tetrone (6a, b).