Acid-catalyzed rearrangement of 9-hydroxyfuranoeremophilanes to eremophilanlactones

Article abstract of DOI:10.1002/hlca.19960790609

9-Hydroxyfuranoeremophilanes 1-3 are the main components of freshly harvested rhizomes of P. hybridus (furanopetasin chemovar). They easily and quantitatively rearrange in the presence of traces of acid to give an epimeric mixture of 8-H-eremophilanlactones 4-6 (eremophilenolides). Besides subsequent oxidation, this is the most important reaction occurring during drying and storage of rhizomes of P. hybridus. A reasonable mechanism of the rearrangement is presented, and spectroscopic structure elucidation of 8-H-eremophilanlactones is discussed.