Biosynthesis of tetraoxygenated phenylphenalenones in Wachendorfia thyrsiflora

The Intramolecular Diels-Alder Reaction of Diarylheptanoids — Quantum Chemical Calculation of Structural Features Favoring the Formation of Phenylphenalenones

“…Oxygen functionalities play an important role in the formation of phenylphenalenones from their open-chain diarylheptanoid precursors [12]. The oxidation stage of the functional groups affects the electron density at the corresponding carbon atoms of the aromatic ring A and in the C 7 -chain, and seems to facilitate cyclization to phenylphenalenones.…”

“…The oxidation pattern of ring A, i.e., the hydroxyketone or dihydroxy moiety at C-1/C-2, is a common feature of anigorufone ( Figure 1) and most other phenylphenalenones. During biosynthesis, this ortho-dioxygenation pattern is retained from ring A of the open-chain diarylheptanoid precursor [12]. The two oxygen substituents in the ortho position (C-3'/C-4') of linear diarylheptanoids seem to be required or at least beneficial for the intramolecular DA cyclization because they are withdrawing electrons from the dienophile double bond (i.e., C-5'/C-6') (structural criterion I).…”

“…The conversion could proceed either by chemical reaction in vitro [10], starting from compound 1a, or in vivo after administration to plant material [11]. [2][3][4][5][6][7][8][9][10][11][12][13] C]1-(3,4-Dihydroxyphenyl)-7-phenylhepta-4,6-dien-3-one (1a), when administered to cultured roots of Anigozanthos preissii, was smoothly converted to [8][9][10][11][12][13] C]anigorufone [11]. …”

Publisher's Note

“…Phenylphenalenones are a characteristic class of secondary metabolites occurring in the monocotyledoneous plant families Haemodoraceae, Pontederiaceae, Strelitziaceae and Musaceae (Munde et al, 2013). They are polycyclic aromatic compounds consisting of a tricyclic phenalene core structure with a keto functional group and a lateral phenyl ring (ring D) (see structure in Table 1).…”

“…In vitro root cultures of A. preissii and Wachendorfia thyrsiflora (both belonging to the Haemodoraceae plant family), which are suitable biological systems for studying the biosynthesis of phenylphenalenones (Hölscher and Schneider, 1995b;Schmitt et al, 2000;Munde et al, 2013), produce pairs of phenylpropanoids and phenylphenalenones with corresponding methoxy-substituted phenyl ring substitutions. Here we report the 1 H NMR and HPLCguided identification of phenylpropanoic acids using an isotope dilution approach.…”