Abstract:

Using A and B as the prototypical structure, eleven 1,5-benzothiazepine derivatives 3a—3k were synthesized and evaluated for their antifungal activity against C. albicans and C. neoformans via the disk diffusion method. The results showed that benzothiazepines 3a, 3b and 3d—3f had good antifungal activity against C. neoformans, compound 3c had moderate activity, and 7-chloro-substituted analogues 3g—3k were weakly active or inactive. In addition, all of the benzothiazepines 3a—3k were almost inactive against C. albicans. Furthermore, compounds 3a, 3b and 3d—3f, which had good antifungal activities, were subjected to further pharmacological evaluation, including determining the dose dependence of the antifungal activity, minimum inhibitory concentration(MIC) and minimum fungicidal concentration(MFC) against C. neoformans. The results showed that the MIC and MFC values for above compounds were much lower than those of fluconazole. In order to examine the structural features responsible for the antifungal activity of compounds 3a—3f, four series of 1,5-benzothiazepine derivatives 4a—4f, 5a—5f, 6a—6f and 7a—7c were synthesized and screened for their antifungal activity. The results demonstrated that the methoxycarbonyl/ethoxycarbonyl group at the 2 position and imine moiety on the seven-membered ring of benzothiazepines 3a—3f was critical to their biological activity. The results also indicated that replacement of sulfur atom in the molecules with nitrogen or oxygen atom led to decrease in activity of this series of compounds.

Key words: 1,5-Benzothiazepine, Antifungal activity, Structure-activity relationship