New acrylamide-sulfisoxazole conjugates as dihydropteroate synthase inhibitors.

New functionalized acrylamide derivatives bearing sulfisoxazole moiety were designed to target bacterial dihydropteroate synthase (DHPS). The in vitro antimicrobial activities of these compounds were assessed. The E-configuration of compound 5b was proved by single crystal X-ray analysis. Compounds 5g and 5h displayed double the activity of ampicillin against B. subtilis. Also, 5h was two times more active than gentamycin against E. coli. Interestingly, compounds 5f-g, 7c, 8a, 8c exhibited two folds the potency of amphotericin B against S. racemosum while 5h displayed three folds the activity of amphotericin B against S. racemosum. Most of the synthesized compounds showed superior activities to the parent sulfisoxazole and were non-toxic to normal cells. DHPS is confirmed to be a putative target for our compounds via antagonizing their antibacterial activity by the folate precursor (p-aminobenzoic acid) and product (methionine) on E. coli ATCC 25922. Docking experiments against DHPS rationalized the observed antibacterial activity. Additionally, compound 5g was evaluated as a selective targeting vector for 99mTc that showed a remarkable uptake and targeting ability towards the infection site that was induced in mice.