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Keywords
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Astrodaucus orientalis, Apiaceae, sesquiterpene lactone, Astrodaucane, Germacryl
cation, Eudesmane,
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Abstract
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Four sesquiterpene lactones, astrodaucanolide A-D (1-4) with unique structures, toghether with
two known phenylpropanoid esters (5 and 6) were isolated from a flower extract of Astrodaucus
orientalis. The structures were established by 1D and 2D NMR spectroscopy and high-resolution
mass spectrometry (HRESIMS), and the absolute configuration of 1-4 was determined by
electronic circular dichroism (ECD). Compounds 1-4 novel architecture represents a new class
of sesquiterpenes with new skeleton. A putative biosynthetic pathway for their scaffold is
proposed with a germacryl cation as the precursor. The suggested biosynthesis pathway is similar
to that of eudesmane sesquiterpenes with a different direction of protonation which then leads to
the new skeleton, named astrodaucane by the 1,2-methyl migration.
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