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A series of new 1,3,4‐oxadiazin‐5(6H)‐one derivatives (6a–n) of dehydroabietic acid were designed and synthesized as potential antimicrobial and antitumor agents. Their structures were characterized by IR, 1H NMR, 13C NMR, MS, and elemental analyses. All the title compounds were evaluated for their antimicrobial activity against four bacterial and three fungal strains using the serial dilution method. Among them, compound 6e showed the highest antibacterial activity against Bacillus subtilis with a minimum inhibitory concentration (MIC) value of 1.9 μg/mL. In addition, the in vitro cytotoxic activities of the title compounds were also assayed against three human carcinoma cell lines (MCF‐7, SMMC‐7721, and HeLa) through the MTT colorimetric method. As a result, compounds 6b, 6g, 6k, and 6m exhibited significant inhibition against at least one cell line with IC50 values below 10 μM. Compound 6m was especially found to be the most potent derivative with IC50 values of 2.26 ± 0.23, 0.97 ± 0.11, and 1.89 ± 0.31 μM against MCF‐7, SMMC‐7721, and HeLa cells, respectively, comparable to positive control etoposide. [ABSTRACT FROM AUTHOR]

A series of new carbazole derivatives of ursolic acid were designed and synthesized in an attempt to develop potent antimicrobial or antitumor agents. Their structures were confirmed by using IR, HRMS and 1 H NMR analysis. All the synthesized compounds were evaluated for their antimicrobial activity against four bacterial and three fungal strains using serial dilution method. Compounds 3a , 3b , 4a , 4b and 5a – f exhibited significant antibacterial activity against at least one tested bacteria with MIC values of 3.9–15.6 μg/ml. In addition, the in vitro cytotoxicity of these compounds were also assayed against two human tumor cell lines (SMMC-7721 and HepG2) using MTT colorimetric method. From the results, compounds 5a – e and 5h displayed pronounced cytotoxic activity with IC 50 values below 10 μM. Specially, compound 5e was found to be the most potent compound with IC 50 values of 1.08 ± 0.22 and 1.26 ± 0.17 μM against SMMC-7721 and HepG2 cells, respectively, comparable to those of doxorubicin. In addition, compound 5e showed reduced cytotoxicity against noncancerous LO2 cells with IC 50 value of 5.75 ± 0.48 μM. [ABSTRACT FROM AUTHOR]