A pyran-2-one and four meroterpenoids from Thapsia transtagana and their implication in the biosynthesis of transtaganolides

Four meroterpenoids and a prenylated pyran-2-one (2) along with the known compounds 7-O-geranylscopoletin (1), and thapsitranstagin have been isolated from the roots of Thapsia transtagana. The presence of 1 and 2 supports the biogenetic hypothesis that transtaganolides, a group of bioactive metabolites, are meroterpenoids which come from an O-prenylated coumarin via successive pericyclic reactions.