Synthesis of Enantiomerically Enriched Dimers of Vinylphenols by Tandem Action of Laccases and Lipases

The tandem use of laccases and lipases has been exploited for the simple preparative synthesis of enantiomerically enriched dimeric phenols. Laccase-catalyzed oxidation of isoeugenol (1) and vinylguaiacol (7) in biphasic systems gave as main products the racemic compounds 6 and 8, possessing structures similar to the beta-5 dimers found in lignin. The synthesis of enantiomerically enriched 6 and 8 could be achieved by alcoholysis reactions catalyzed by commercial preparations of lipases in organic solvents. Although the E values were quite low (due to the "remote" stereocenters to be discriminated), the enantio-complementary behavior of the tested lipases allowed the simple isolation of the target compounds with ee up to 90%. It is noteworthy that these results have been achieved in vitro exploiting commercially available enzymes, without using the so-called "dirigent" proteins evolved by nature to direct the enantioselective coupling of phenols in vivo.