Biosynthesis of angular furanocoumarins

Abstract

The biosynthesis of angular furanocoumarins from umbelliferone in Angelica archangelica and Heracleum lanatum has been shown by isotope studies to parallel that of linear furanocoumarins, via the dihydrofuranocoumarin columbianetin. Angelicin, the first angular furanocoumarin formed, is converted by hydroxylation and O-alkylation to a range of substituted angelicins. A detailed biosynthetic route to angular furanocoumarins, consistent with known stereochemistry, is proposed. By variations of this pathway, it is possible to account for the elaboration of pyranocoumarins, furanoquinoline alkaloids, furanochromones, and possibly other plant products which frequently co-occur with furanocoumarins.A separation of furanocoumarins by column absorption chromatography on silicic acid, and a synthesis of [2-14C]angelicin, are described.