• antibacterial activity;
  • glycosyltransferase;
  • isatin derivatives;
  • STD-NMR;
  • virtual screening

Peptidoglycan glycosyltransferase (PGT) has been shown to be an important pharmacological target for the inhibition of bacterial cell wall biosynthesis. Structure-based virtual screening of about 3 000 000 commercially available compounds against the crystal structure of the glycosyltransferase (GT) domain of the Staphylococcus aureus penicillin-binding protein 2 (S. aureus PBP2) resulted in identification of an isatin derivative, 2-(3-(2-carbamimidoylhydrazono)-2-oxoindolin-1-yl)-N-(m-tolyl)acetamide (4) as a novel potential GT inhibitor. A series of 4 derivatives were synthesized. Several compounds showed more active antimicrobial activity than the initial hit compound 4, in particular 2-(3-(2-carbamimidoylhydrazono)-2-oxoindolin-1-yl)-N-(3-nitrophenyl)acetamide (4l), against Gram-positive Bacillus subtilis and S. aureus with MIC values of 24 and 48 μg/mL, respectively. Saturation transfer difference (STD) NMR study revealed that there is a binding contact between 4l and the GT domain of S. aureus PBP2. Competitive STD-NMR further proved that 4l and moenomycin A bind to GT domain in a competitive manner. Molecular docking study suggests a potential binding pocket of 4l in the GT domain of S. aureus PBP2. Taken together, compound 4l would provide a new scaffold for further development of potent GT inhibitors.