Feeding of (2,3,4,5,6-(13) C5 )mevalonolactone to the fungus Hypomyces odoratus resulted in a completely labeled sesquiterpene ether. The connectivity of the carbon atoms was easily deduced from a (13) C,(13) C COSY spectrum, revealing a structure that was different from the previously reported structure of hypodoratoxide, even though the reported (13) C NMR data matched. A structural revision of hypodoratoxide is thus presented. Its absolute configuration was tentatively assigned from its co-metabolite cis-dihydroagarofuran. Its biosynthesis was investigated by feeding of (3-(13) C)- and (4,6-(13) C2 )mevalonolactone, which gave insights into the complex rearrangement of the carbon skeleton during terpene cyclization by analysis of the (13) C,(13) C couplings.
Keywords: NMR spectroscopy; biosynthesis; isotopic labeling; structure elucidation; terpenoids.
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