Complex Flavonoids from Pityrogramma Frond Exudates: Synthesis of Two Flavones with C—C-Linked Dihydrocinnamoyl Substituents

Abstract

Complex flavonoids that are typical for the frond exudate in ferns of the genus Pityrogramma are surveyed to demonstrate their close structural relation. Two such compounds, isolated earlier from the exudate of Pityrogramma calomelanos var. aureoflava are prepared by an unambiguous synthesis. Direct comparisons of the synthetic products, namely P-(5,7.4′-trihydroxy-8-yl)-β- phenylpropionic acid and its methyl ester, show them to be identical with the natural products. The structures deduced previously for these compounds by spectroscopic methods are thus confirmed.