The Furan Shuffling Hypothesis: A Biogenetic Proposal for Eremophilane Sesquiterpenoids

摘要

Based on the structural similarities of the recently isolated eremophilane-type sesquiterpenoids microsphaeropsisinB and C and the iso-eremophilane periconianoneC, a revised biogenetic hypothesis for C8-C11-connected iso-eremophilanes is presented and corroborated by strong experimental evidence. The first enantioselective total syntheses of microsphaeropsisinB and C were achieved starting from a known intermediate, whose synthesis was elaborated previously in the total synthesis of periconianoneA, and in a total of 15 steps starting from gamma-hydroxy carvone. Mild reaction conditions for the subsequent alpha-ketol rearrangement not only resulted in the herein proposed conversion of microsphaeropsisinB into periconianoneC, but also in the conversion of microsphaeropsisinC into 4-epi-periconianoneC.