Efficient and convenient synthesis, characterization, and antimicrobial evaluation of some new tetracyclic 1,4-benzothiazines

In the present study, 20 new tetracyclic 1,4-benzothiazines (<b>4a</b>–<b>4 t</b>) were conveniently synthesized in good yields and characterized by different spectral and physical techniques. The in vitro antimicrobial evaluation of the synthesized benzothiazine derivatives was performed by serial dilution against two Gram-positive bacteria [<i>Bacillus subtilis</i> (MTCC 441) and <i>Staphylococcus epidermidis</i> (MTCC 6880)], two Gram-negative bacteria [<i>Escherichia coli</i> (MTCC 1652) and <i>Pseudomonas aeruginosa</i> (MTCC 424)], and two fungal strains [<i>Candida albicans</i> (MTCC 227) and <i>Aspergillus niger</i> (MTCC 8189)]. The derivatives <b>4 l</b> and <b>4 t</b> were found to be more potent than standard drug, i.e., fluconazole, against <i>A. niger</i> and <i>C. albicans</i>, respectively.

本研究中，20种新型四环类1,4-苯并噻嗪（1,4-benzothiazines）衍生物（4a~4t）以较高收率便捷合成，并通过多种光谱及物理手段完成结构表征。本研究采用系列稀释法，对所合成的苯并噻嗪衍生物开展体外抗菌活性评价，测试菌株涵盖2株革兰氏阳性细菌：枯草芽孢杆菌（Bacillus subtilis，MTCC 441）、表皮葡萄球菌（Staphylococcus epidermidis，MTCC 6880）；2株革兰氏阴性细菌：大肠埃希菌（Escherichia coli，MTCC 1652）、铜绿假单胞菌（Pseudomonas aeruginosa，MTCC 424）；以及2株真菌：白色念珠菌（Candida albicans，MTCC 227）、黑曲霉（Aspergillus niger，MTCC 8189）。活性测试结果显示，衍生物4l与4t分别对黑曲霉与白色念珠菌的抗菌活性优于对照药物氟康唑（fluconazole）。