New reagent for oxidative phenol coupling. The transformation of the monocyclic spermine base (S)-dihydroxyverbacine to the bicyclic alkaloid (S,S,S)-aphelandrine by cell free extract of barley seedlings

The soluble protein fraction of barley seedlings (Hordeum vulgare, Gramineae) in the presence of O2 stereoselectively catalyzes the intramolecular phenol coupling of the monocyclic spermine base (S)-dihydroxyverbacine to the bicyclic aphelandrine in preparative yield. The expected microsomal-bond cytochrome P-450 enzyme system does not contribute to this reaction. The nature of the involved biocatalyst still remains uncertain. The catalytic potential of the cell free extract of barley seedlings suggests its possible use as an efficient tool for large scale stereoselective chemoenzymatic synthesis of aphelandrine type alkaloids.