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

A new dimeric eudesmane sesquiterpenoid with an unreported 6/6/5/6/6
fused carbon skeleton, echingridimer A (1), and five
monomers (2–6), including two new
compounds (2 and 3), were isolated from
the roots of Echinops grijsii. Their
structures and absolute configurations were elucidated by comprehensive
spectroscopic analyses and confirmed by X-ray crystallography or electronic
circular dichroism spectra. Compound 1 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 1–6 was briefly discussed. The oxaspiro dimer (1) not only
showed stronger aphicidal activity than closely related monomeric
compounds (2–6) 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.