Syntheses of 3-Substituted 1-Methyl-6-phenylpyrimido[5, 4-e]-1, 2, 4-triazine-5, 7(1H, 6H)-diones (6-Phenyl Analogs of Toxoflavin) and Their 4-Oxides, and Evaluation of Antimicrobial Activity of Toxoflavins and Their Analogs

Abstract

6-Phenyl analogs of toxoflavin {1-methyl-6-phenylpyrimido[5, 4-e]-1, 2, 4-triazine-5, 7(1H, 6H)-diones} (7a-f) and their 4-oxides (8a-f) were synthesized by nitrosative or nitrative cyclization of the aldehyde hydrazones (6a-f) of 6-(1-methylhydrazino)-3-phenyluracil (5). Both sets of compounds, 7a-f and 8a-f, gave the corresponding 1-demethyl derivatives (10a-f) upon treatment with nucleophiles such as dimethylformamide (DMF) and acetic acid under heating. The activities of toxoflavins (1a-e), toxoflavin 4-oxides (3a-e) and their 6-phenyl analogs (7a-f and 8a-f) against a variety of bacterial and fungal strains were examined. Most of the compounds showed strong inhibitory activities against gram-positive bacteria. Among the compounds, 1c, 1d, 1e, and 3c exhibited the strongest inhibitions of Micrococcus lutea (0.5 μg/ml minimal growth-inhibitory concentration) and Staphylococcus aureus 4R (1 μg/ml), as well as Bacillus subtilis and Staphylococcus aureus (1-2 μg/ml). Most of the compounds had strong antifungal activity (2-100 μg/ml minimal growth-inhibitory concentration) against Candida albicans and Saccharomyces cerevisiae.