Novel 2-Thioxanthine and Dipyrimidopyridine Derivatives: Synthesis and Antimicrobial Activity

Several fused imidazolopyrimidines were synthesized starting from 6-amino-1-methyl-2-thiouracil (1) followed by nitrosation, reduction and condensation with different aromatic aldehydes to give Schiff's base. The dehydrocyclization of Schiff's bases using iodine/DMF gave Compounds 5a-g. The methylation of 5a-g using a simple alkylating agent as dimethyl sulfate ((CH₃)₂SO₄) gave either monoalkylated imidazolopyrimidine 6a-g at room temperature or dialkylated derivatives 7a-g on heating 6a-g with ((CH₃)₂SO₄). On the other hand, treatment of 1 with different aromatic aldehydes in absolute ethanol in the presence of conc. hydrochloric acid at room temperature and/or reflux with acetic acid afforded bis-5,5́-diuracylmethylene 8a-e, which cyclized on heating with a mixture of acetic acid/HCl (1:1) to give 9a-e. Compounds 9a-e can be obtained directly by refluxing of Compound 1 with a mixture of acetic acid/HCl. The synthesized new compounds were screened for antimicrobial activity, and the MIC was measured.