Echingridimer A, an Oxaspiro Dimeric Sesquiterpenoid with a 6/6/5/6/6 Fused Ring System from and Aphicidal Activity Evaluation.

A new dimeric eudesmane sesquiterpenoid with an unreported 6/6/5/6/6 fused carbon skeleton, echingridimer A (), and five monomers (-), including two new compounds ( and ), were isolated from the roots of . Their structures and absolute configurations were elucidated by comprehensive spectroscopic analyses and confirmed by X-ray crystallography or electronic circular dichroism spectra. Compound represents the first example of a 3,15'-linked Michael-type adduct of two eudesmanes, which feature a unique 1-oxaspiro[4.5]decan moiety. The plausible biogenetic pathway for - was briefly discussed. The oxaspiro dimer () not only showed stronger aphicidal activity than closely related monomeric compounds (-) and the commercial aphicide pymetrozine but also exhibited remarkable insecticide activity against a broad range of aphids, thus could be used as a potential biobased insecticide to suppress aphids.