Recent Developments in Enzymatic Asymmetric C-C Bond Formation

Some of the recent developments in enzymatic asymmetric C-C bond formation are described in this review. The close relationship of biocatalysis and biosynthesis is highlighted with a special emphasis on diversity and biogenesis. One focus of this review is the creation of tetrasubstituted carbon stereocenters. Members of the supposedly well-known aldolase and hydroxynitrile lyase enzyme families possess the ability to catalyze the formation of tertiary alcohols. In the case of aldolases, this can occur through intramolecular cyclization or intermolecular asymmetric C-C bond formation. Thiamine diphosphate-dependent YerE has been identified as a potent catalyst for the acyloin condensation with ketones as acceptor substrates. C-1 transformations such as methylation or carboxylation are catalyzed in an asymmetric manner by enzymes from different classes, for example S-adenosylmethionine-dependent (radical) enzymes or NADPH-dependent oxidoreductases. Insights from biosynthetic and mechanistic studies of enzymatic reactions proceeding via radical intermediates give valuable hints towards possible applications in biocatalysis. Still, the oxygen sensitivity of many of these biocatalysts poses a considerable challenge for practical applications.