Biosynthesis of cyclic bis(bibenzyls) in Marchantia polymorpha

Using sterile thallus tissue of Marchantia polymorpha, the biosynthesis of the cyclic bis(bibenzyl) marchantin A was investigated. The synthesis of the radioactively and C-13-labelled precursors for the application experiments is described. Feeding experiments showed that rings A and C of the marchantin molecule are derived from the benzene ring of L-phenylalanine via trans-cinnamic acid and p-coumaric acid. Further application of C-13-labelled precursor with subsequent C-13 NMR spectroscopy proved that dihydro-p-coumaric acid is an intermediate in marchantin biosynthesis. A phenylpropane/polymalonate pathway using dihydro-p-coumaric acid and acetate/malonate is proposed for the biosynthesis of the bibenzyl monomers which were confirmed to be the building blocks of the marchantin molecule. The bibenzyls in turn are coupled in a unique way to form the bis(bibenzyl) structure. (C) 1998 Elsevier Science Ltd. All rights reserved.