Solid phase combinatorial synthesis of benzothiazoles and evaluation of topoisomerase II inhibitory activity Original Research Article

To investigate one possible mechanism of action of the cytotoxic activity of benzothiazoles, we synthesized 2-(substituted-phenyl)benzothiazoles and evaluated their ability to inhibit topoisomerase II activities. Solid phase combinatorial method using trityl resin was employed and benzothiazole derivatives with various substitution on 2′-, 3′-, or 4′-position of phenyl group were obtained in ca. 30 mg scale (7–96% yield). Most of the compounds synthesized exhibited topoisomerase II inhibitory activity at 100 μM. 2-(3-Amino-4-methylphenyl)benzothiazole showed high activity (IC50 = 71.7 μM), comparable to etoposide (IC50 = 78.4 μM).