As a novel class of IKKβ inhibitors, a series of tricyclic furan derivatives was designed and synthesized based on the structure of known thiophene IKKβ inhibitors. Among the various fused furan derivatives synthesized, a benzothieno [3, 2-b] furan derivative 13a displayed potent inhibitory activity towards IKKβ in enzymatic and cellular assays. The potent inhibitory activity originates from an intramolecular non-bonded S… O interaction which was ...