Ralfuranone Thioether Production by the Plant Pathogen Ralstonia solanacearum

Ralfuranones are aryl-substituted furanone secondary metabolites of the Gram-negative plant pathogen Ralstonia solanacearum. New sulfur-containing ralfuranone derivatives were identified, including the methyl thioether-containing ralfuranone D. Isotopic labeling in vivo, as well as headspace analyses of volatiles from R. solanacearum liquid cultures, established a mechanism for the transfer of an intact methylthio group from L-methionine or α-keto-γ-methylthiobutyric acid. The methylthio acceptor molecule ralfuranone I, a previously postulated biosynthetic intermediate in ralfuranone biosynthesis, was isolated and characterized by NMR. The highly reactive Michael acceptor system of this intermediate readily reacts with various thiols, including glutathione.