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As part of our studies focused on the design and synthesis of new antimicrobial agents a series of 7-fluoro-3,4-dihydro-2H-1,4-benzothiazine derivatives (4a-4f, 4h) and 7-fluoro-2H-1,4-benzothiazin-3(4H)-one analogues (4j-4o) were synthesized and evaluated for their in vitro inhibitory activity against a representative panel of Gram-positive and Gram-negative bacteria strains and also toward selected fungi species. These compounds were prepared in one step from chloro-substituted-2-amino-5-fluorobenzenethiol 6a-6c. The biological screening identified in compounds 4a, 4j and 4l the most promising results of both series showing an interesting antimicrobial activity. Our antibiotic investigation was also completed by testing the key intermediates 6a-6c. Surprisingly, 6a-6c emerged as the compounds exhibiting the highest antimicrobial activity by possessing a remarkable antibacterial effect against the Gram-positive strains with MIC (minimal inhibitory concentration) values between 2 and 8 µg/mL and the fungi panel with MIC values between 2 and 8 µg/mL. These results may prove useful in the design of a novel pool of antimicrobial agents.

Enterococcus faecalisis a Gram-positive commensal inhabitant of the intestinal tract of humans, animals, and insects. However, it is also an opportunistic pathogen and has emerged as a leading cause of hospital-acquired extraintestinal infections. Fluoroquinolones have been frequently used to treatE. faecalisinfections, and the emergence of fluoroquinolone-resistantE. faecalisstrains has recently been reported in several countries. Thus, the identifications of new antibiotics specifically directed toE. faecalismay be envisaged. In this paper, a new series ofN-1,3-benzothiazol-2-ylbenzamides have been designed, synthesized, and evaluated for theirin vitroantimicrobial activities. Among the tested compounds,3iwas active againstE. faecalis.

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The synthesis of some pyrrolo[1,2,3‐de]‐1,4‐benzothiazine derivatives by using a modified Bischler type cyclization of N‐(2,2‐diethoxyethyl)‐2H‐1,4‐benzothiazines as a crucial step is described. The alternative approach based on Friedel‐Crafts alkylation of the N‐(2‐chloroethyl)‐2H‐1,4‐benzothiazines is shown to be impractical due to the low yield obtained.