Nardochinoids A–C, Three Dimeric Sesquiterpenoids with Specific Fused-Ring Skeletons from Nardostachys chinensis

Three unusual sesquiterpenoid dimers, nardochinoids A–C (1–3), were isolated from Nardostachys chinensis Batal. Compound 1 features a rare fused 3,8-dioxatricyclo­[7.2.1.01,6]­dodecane-11-one ring system, compound 2 is the first nitrogen-containing nornardosinane–aristolane sesquiterpene conjugate, and compound 3 represents the first example of the dimer of a nornardosinane and a nardosinane sesquiterpene. Their structures were characterized by NMR spectroscopic methods and X-ray single-crystal diffraction analysis. Compound 3 showed significant anti-inflammatory activities.