(−)-Dehydroxymethylepoxyquinomicin ((−)-DHMEQ, 1) is a specific inhibitor of NF-κB. It binds to SH group in the specific cysteine residue of NF-κB components with its epoxide moiety to inhibit DNA binding. In the present research, we have designed and synthesized an epoxide-free analog called (S)-β-salicyloylamino-α-exo-methylene-ƴ-butyrolactone (SEMBL, 3). SEMBL inhibited DNA binding of NF-κB component