Synthesis and Cytotoxic and Antiplatelet Activities of Dibenzofuran- and Carbazole-Substituted Oximes

The dibenzofuran- and carbazole-substituted oximes or methyloximes 5-10 were prepared and evaluated for their cytotoxic and antiplatelet activities. These compounds were synthesized via alkylation of dibenzofuran-2-ol or 9H-carbazol-2-ol with α-halocarbonyl reagents, followed by reaction with NH₂OH or NH₂OMe (Scheme). A preliminary anticancer assay indicated that the oxime-type dibenzofuran derivatives 5 and 7a-d are active, while the corresponding oxime ethers 9h and 9c are inactive at the same concentration. Therefore, a H-bond-donating group seems to be crucial for cytotoxicity. Among the compounds tested, 2-[(dibenzo[b,d]-furan-2-yl)oxy]-1-(4-methoxyphenyl)ethan-1-one O-methyloxime (9c) exhibited potent inhibitory activity against platelet aggregation induced by arachidonic acid, with an IC₅₀ value of 14.87 μM, without being cytotoxic at a concentration of 100 μM.