Regioselective dimerization of ferulic acid in a micellar solution

Dehydrodimers of hydroxycinnamates play an important role in the cross-link ing of plant cell walls. An aqueous solution of quaternary ammonium salts w ith a long aliphatic chain is known to spontaneously organize itself into m icelles with the ionic part at the outer sphere. It is shown that regioisom eric ferulic acid dehydrodimers can be obtained in one step from trans-feru lic acid after attachment to these micelles and using the biomimetic peroxi dase-H2O2 system. The surfactant hexadecyltrimethylammonium hydroxide yield ed trans-4-(4-hydroxy-3-methoxybenzylidene)-2-(4-hydroxy-3-methoxyphenyl)-5 -oxotetrahydrofuran-3-carboxylic acid (25%), (E,E)-4,4 ' -dihydroxy-5,5 ' d imethoxy-3,3 ' -bicinnamic acid (21%), and trans-5-[(E)-2-carboxyvinyl]-2-( 4-hydroxy-3-methoxyphenyl)-7-methoxy-2,3-dihydrobenzofuran-3-carboxylic aci d (14%), whereas the surfactant tetradecyltrimethyl-ammonium bromide gave 4 -cis, 8-cis-bis(4-hydroxy-3-methoxyphenyl)-3,7 octane-2,6-dione (18%) as th e main product. The use of micelles appears to be not only a new way to syn thesize regioisomeric ferulic acid dehydrodimers but may also help to under stand the regiospecificity of dimeric hydroxycinnamate formation in vivo.