Chromone-Fused Cytosine Analogues: Synthesis, Biological Activity, and Structure–Activity Relationship

The preparation of a series of novel chromone-fused cytosine analogues, i.e., chromeno[2,3-d]pyrimidines has been carried out from substituted 2-amino-4-oxo-4H-chromene-3-carbonitriles with urea, thiourea, and guanidine under different reaction conditions. These chromone-fused cytosine analogues were evaluated for their in vitro activity against Mycobacterium tuberculosis H37Rv strain and different microbial pathogenic strains in cell culture for their structure–activity relationships, respectively. Among the synthesized compounds, 2d, 3a, and 4e showed better results against Mycobacterium tuberculosis H37Rv. The compounds 2a, 2b, and 3a showed potential antibacterial activity against E. coli and P. aeruginosa, while the majority of compounds were found to be active against S. aureus as compared to ampicillin. The synthesized cytosine analogues having an imine (–C&dbnd;NH) have been less sensitive to the bacterial and fungal strains but have a more beneficial effect on Mycobacterium tuberculosis H37Rv.