An enantioselective synthesis of (+)-8-epi-xanthatin hinging on a chiral phosphoric acid catalyzed tandem allylboration/lactonization reaction is reported. With (+)-8-epi-xanthatin as the precursor, the collective synthesis of a series of synthetically challenging xanthanolides was also accomplished. Among them, xanthipungolide, one of the most complex xanthanolide monomers, was accessed through a bioinspired tandem double-bond isomerization/6π electronic cyclization/intramolecular Diels-Alder reaction, and pungiolides A, B, D, E, and L-N, a group of xanthanolide dimers, were assembled through a bioinspired Diels-Alder dimerization followed by late-stage diversification.
Keywords: Diels-Alder reaction; biomimetic synthesis; ene reaction; photochemical reactions; terpenoids.
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