Synthesis of Substituted 6-Anilinouracils and Their Inhibition of DNA Polymerase IIIC and Gram-Positive Bacterial Growth

Abstract

Certain substituted 6-anilinouracils are potent and selective inhibitors of Gram+ bacterial DNA polymerase IIIC (pol IIIC). In addition, analogues with 3-substituents in the uracil ring have potent antibacterial activity against Gram+ organisms in culture. In an attempt to find optimal anilino substituents for pol IIIC binding and optimal 3-substituents for antibacterial activity, we have prepared several series of 3-substituted-6-aminouracils and assayed their activity against pol IIIC from Bacillus subtilis and a panel of Gram+ and Gram- bacteria in culture. The 6-(3-ethyl-4-methylanilino) group and closely related substituent patterns maximized pol IIIC inhibition potency. Among a series of 3-(substituted-butyl)-6-(3-ethyl-4-methylanilino)uracils, basic amino substituents increased pol IIIC inhibition, but decreased antibacterial activity. The most potent antibacterials were simple hydroxybutyl and methoxybutyl derivatives, and hydrophobically substituted piperidinylbutyl derivatives.

Biological Characterization of Novel Inhibitors of the Gram-Positive DNA Polymerase IIIC Enzyme

“…The MICs of the compounds described here for gram-positive cocci were found to be, at best, in the range of 4 to 8 g/ml, which is in agreement with data from recent reports describing aminoalkyl substituents at position 3 of the uracil ring (31). It is noteworthy that the MICs of the investigated derivatives somehow seemed to be limited, regardless of the anti-Pol IIIC activity measured in the enzymatic assay; i.e., although the anti-Pol IIIC activities of the compounds could be significantly improved, the antibacterial activities (MICs) of the compounds could not be improved beyond a comparatively modest MIC of 2 g/ml.…”

“…Among the series of linear N-alkyl substituents, the potency seems to correlate with lipophilicity; thus, the highest activity was achieved with N-3 butyl-substituted TMAU (25), whereas the addition of a benzyl group at N-3 significantly reduced the anti-Pol IIIC activity (25), seemingly indicating an unfavorable steric interaction. A recent report (31) has described the more hydrophilic N-3-piperidinylbutyl derivative as a potent Pol IIIC inhibitor. Our work with this compound class was based on the hypothesis that an energetically favorable interaction with the Pol IIIC enzyme could be achieved by elaboration of the N-3 substituent, which in turn would lead to improved antibacterial potency.…”

“…The identification of novel classes of antibacterial substances that inhibit a new or unexploited target is expected to facilitate novel therapeutic approaches for the treatment of infections caused by multiresistant pathogens. 6-Anilinouracils (AUs) have been described in the literature (1,9,24,25,27,28,31) and in patent applications (3,7) as a novel antibacterial class showing selective inhibition of DNA polymerase IIIC (Pol IIIC; formerly Pol III), the enzyme required for the replication of chromosomal DNA in gram-positive organisms with low GϩC contents (29).…”

“…The enhanced antibacterial activities of the compounds with the N-3 side chain alkyl substituents compared to those of N-3-unsubstituted molecules have been described (9,25). Moreover, more complex aminoalkyl substituents have also been described in this position of the molecule (31).…”

Synthesis and Antimicrobial Studies of New Trifluoromethylpyrimidine Analogues

“…Their impact is particularly large in developing countries due to the relative unavailability of medicines, while the excessive use of antimicrobial drugs has led to the emergence of widespread bacterial resistance [1]. In 2003, a number of substituted pyrimidines were synthesized and intensively studied as potent and selective inhibitors of Gram positive bacterial DNA polymerase IIIC [2]. Over the last decades, development of drug resistance as well as the appearance of undesirable side effects of some antibiotics [3] has initiated the search for new antimicrobial agents to overcome some of the disadvantages of the existing drugs [4].…”