6-anilinouracil-based inhibitors of Bacillus subtilis DNA polymerase III: Antipolymerase and antimicrobial structure-activity relationships based on substitution at uracil N3

6-Anilinouracils (6-AUs) are dGTP analogues which selectively inhibit the D NA polymerase III of Bacillus subtilis and other Gram-positive bacteria. To enhance the potential of the 6-AUs as antimicrobial agents, a structure-ac tivity relationship was developed involving substitutions of the uracil N3 position in two 6-AU platforms: 6-(3,4-trimethyleneanilino)uracil (TMAU) an d 6-(3-ethyl-4-methylanilino)uracil (EMAU). Series of N3-alkyl derivatives of both 6-AUs were synthesized and tested for their ability to inhibit puri fied B. subtilis DNA polymerase III and the growth of B. subtilis in cultur e. Alkyl groups ranging in size from ethyl to hexyl enhanced the capacity o f both platforms to bind to the polymerase, and with the exception of hexyl , they also significantly enhanced their antimicrobial potency. N3 substitu tion of the EMAU platform with more hydrophilic hydroxyalkyl and methoxyalk yl groups marginally enhanced anti-polymerase III activity but enhanced ant ibacterial potency severalfold. In sum, the results of these studies indica te that the ring N3 of 6-anilinouracils can tolerate substituents of consid erable size and structural variety and, thus, can be manipulated to signifi cantly enhance the antibacterial potency of this novel class of polymerase III-specific inhibitors.