4<i>H</i>‐1‐benzothiopyran‐4‐one‐3‐carboxylic acids and 3,4‐dihydro‐2<i>H</i>‐isothiazolo[5,4‐<i>b</i>benzothiopyran‐3,4‐diones as quinolone antibacterial analogs

Abstract

Abstract The endocyclic replacement of a nitrogen atom at the 1‐position of quinolone antibacterial nucleus with a sulfur atom was investigated. A series of 1‐benzothiopyran‐4‐one‐3‐carboxylic acids 14–16 and isothiazolo‐[5,4‐ b ][1]benzothiopyran‐3,4‐diones 22–24 , suitably functionalized with a fluorine atom at C‐6 and heterocyclic base at C‐7, were prepared. The antibacterial evaluation of the target compounds showed an activity comparable to that of nalidixic acid for compounds 14–16 , while an increased activity against gram‐positive bacteria was observed for compounds 22–24 .