Naphthofuran precursors of sesquiterpenoid aldehydes in diseased Gossypium

Abstract

Crude terpenoid fractions from stele tissues of Gossypium barbadense infected with Verticillium dahliae contained two prominent compounds that were nonaldehydic, but readily autooxidized to the terpenoid aldehydes hemigossypol and 6-methoxyhemigossypol. Spectral analyses, chemical studies, and comparisons with model compounds showed that these compounds were the sesquiterpenoids 3,4-dihydroxy-5-isopropy]-7-methy]-2 H-naphtho[1,8- bc]furan ( 1a) and 3-hydroxy-5-isopropyl-4-methoxy-7-methyl-2 H-naphtho[1,8- bc]furan ( 1b). The trivial names desoxyhemigossypol and desoxy-6-methoxyhemigossypol are proposed for ( 1a) and ( 1b). The sesquiterpenoid, previously isolated and named vergosin, is apparently desoxy-6-methoxyhemigossypol.