Synthesis and assessment of bisindoles as a new class of antibacterial agents

Antimicrobial screening of an in-house library containing both natural products and synthetic compounds identified a bisindole molecule as a selective antibacterial hit. Further evaluation and structural modification afforded a series of dimeric indole derivatives, most of which showed moderate to good antibacterial activity against two Gram-positive strains Staphylococcus aureus and Bacillus subtilis. Chiral HPLC was employed to separate these racemates and the bioactive differences between the enantiomeric pairs were also assessed and discussed. Three dihalogenaged analogues also showed mild growth inhibition against a drug-resistant S. aureus strain.