The biosynthesis of 8-phenylphenalenones from Eichhornia crassipes involves a putative aryl migration step

Phenylphenalenones with a lateral phenyl ring in unusual 8-position have been isolated from Eichhornia crassipes (Pontederiaceae). The structures were elucidated by spectrometric methods including NMR and MS analysis. The incorporation of two molecules of [1-13C]phenylalanine provides experimental evidence for the biosynthesis via 1,2-aryl migration from an intermediate of the 9-phenylphenalenone type.