Biocatalytic synthesis of optically active oxyfunctionalized building blocks with enzymes, chemoenzymes and microorganisms

In this account, we summarize the highlights of our cooperative research work on the biocatalytic preparation of enantiomerically enriched, oxyfunctionalized substances in the ‘Sonderforschungsbereich (SFB 347): Selektive Reaktionen Metall-aktivierter Moleküle’. The biocatalytic kinetic resolution of secondary hydroperoxides with the metalloenzymes horseradish (HRP) and Coprinus (CiP) peroxidase affords the hydroperoxides and their alcohols in excellent enantiomeric excess. Also the semisynthetic enzyme selenosubtilisin catalyzes effectively the enantioselective reduction of racemic hydroperoxides to produce optically active hydroperoxides and alcohols in high ee values. The asymmetric CH oxidation of long- and medium-chain carboxylic acids by molecular oxygen, catalyzed with the α-oxidase from pea leaves or germinating peas yields enantiomerically pure 2-hydroxy acids. The enzymatic kinetic resolution of racemic 2-hydroxy acids through the enantioselective oxidation by glycolate oxidase (GOX) or the esterification by lipase provides an attractive route to such optically active building blocks. The bacteria Bacillus subtilis and Bacillus megaterium, isolated from topsoil by selective screening with hydrogen peroxide or allylbenzene, are efficient biocatalysts for the enantioselective reduction of racemic hydroperoxides and the asymmetric CH oxidation of alkanes. The latter enzymatic process is to date still difficult to emulate by chemical catalysis.