Synthesis and evaluation of novel fluorinated 2-styrylchromones as antibacterial agents
School of Chemistry, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa; School of Chemical Engineering, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa; Department of Biochemistry, Genetics and Microbiology, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa
A range of fluorinated 2-styrylchromones (5a-g) of which six were new (5a-f) were prepared in three steps using the Baker-Venkataraman rearrangement along with two methoxylated derivatives (5h-i) and a methylenedioxy derivative (5j) and screened for their antibacterial activity using Gram-positive bacteria (Staphylococcus aureus, sciuri, and xylosus as well as Bacillus subtilis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia). The compounds were most effective against B. subtilis followed by S. aureus and a single strain of E. coli (ATCC 25922). Difluorination on the phenyl ring was shown to enhance antibacterial activity, and fluorine substitution at the 6 position was shown to be far superior to substitution at the 7 position. In comparison to tetracycline, the activity indices of the fluorinated styrylchromones ranged from 0.50 to 0.75 against B. subtilis. The crystal structure of 2′-fluoro-2-styrylchromone is also presented, and the molecule was shown to be planar. © 2013 Mehbub Momin et al.