Many interesting compounds with novel structures and possessing biological activitieshave been isolated from soft coral of genus Clavularia.From the soft coral Clavulariaviridis we have isolated eight new diterpenes and a new sterol.Some of them exhibitedantitumor activity.In a continuation of systematic investigation on the chemical con-stituents of soft corals,we isolated a new sesquterpenoid named clavulinin (1) from thesoft coral Clavularia inflata Schenk.Its structure was determined mainly on the basis ofspectral analysis.Clavulinin is a member of elemane-type sesquiterpene acid ester containinga very rare γ-hydroxy-α,β-butalactam system.