A series of dibenzo[b,e]ox(thi)epin-11(6H)-one O-benzoyloximes has been\nsynthesized and structurally elucidated by means of IR, 1H-NMR, 13C-NMR, MS,\nand elemental analysis. The newly developed compounds were screened at\nconcentrations of 200ââ?¬â??25 g/mL for their antibacterial activity against Gram+ve\norganisms such as Methicillin-Resistant Staphylococcus Aureus (MRSA),\nGramââ?¬â??ve organisms such as Escherichia coli (E. coli), and at the same\nconcentration range for their antifungal activity against fungal strain Aspergillus\nniger (A. niger) by the cup plate method. Ofloxacin and ketoconazole\n(10 g/mL) were used as reference standards for antibacterial and antifungal\nactivity, respectively. The dibenzo[b,e]oxepines 6aââ?¬â??c and 6eââ?¬â??h showed low\nantimicrobial activity (MIC 125ââ?¬â??200 g/mL) compared to the reference\nsubstances, whereas a major improvement (MIC 50ââ?¬â??75 g/mL) was achieved\nwith the synthesis of the corresponding bromomethyl derivative 6d. Moreover,\nreplacement of oxygen by its bioisosteric sulfur led to isomeric dibenzo[b,e]thiepine\nderivatives 6g,h which significantly exhibited higher antimicrobial activity\n(MIC 25ââ?¬â??50 g/mL) against all tested culture strains used in the present study,\ndemonstrating that a change of chemical class from dibenzo[b,e]oxepine to\ndibenzo[b,e]thiepine significantly improves the antimicrobial activity. Further\nvariation, such as the oxidation of the thiepine sulfur to the corresponding\nisomeric dibenzo[b,e]thiepine 5,5-dioxide derivative 9, comparatively failed to\nexhibit high activity (MIC 200 g/mL) against S. aureus, E. coli or A. niger.
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