ENZYME-MEDIATED COUPLING OF 3,4-DICHLOROANILINE AND FERULIC ACID - A MODEL FOR POLLUTANT BINDING TO HUMIC MATERIALS

To investigate the incorporation of chloroanilines into humic substances, the reaction of ferulic acid with three different chloroanilines in the presence of a laccase of the fungus Rhizoctonia praticola was investigated. Under the reaction conditions used, chloroanilines alone were not transformed by the laccase, but in the presence of ferulic acid they formed cross-coupling products. The reactivity of anilines decreased with increasing chlorine substitution on the ring. Two dimeric compounds were isolated from the reaction assay of ferulic acid alone. The dimers were found to have phenylcoumaran and lactone structures. After reacting ferulic acid with 3,4-dichloroaniline, two trimers were isolated and identified, providing insight into the reaction mechanism; the two hybrid trimers contained one aniline and two ferulic acid molecules. The formation of the hybrid trimers can be best rationalized by the nucleophilic addition of 3,4-dichloroaniline to quinone methide intermediates produced from the radical coupling of ferulic acid.