The stereoselective reduction of suitably substituted C═C bonds mediated by enzymes, called ene reductases, has received great attention in the last decade. Some successful applications of this biocatalysed procedure to the synthesis of chiral active pharmaceutical ingredients have been reported in the literature. The generation of suitable models to be used for predicting the stereochemical outcome of this kind of reductions is a challenging task. In the last years we have exploited deuterium labelling to investigate the stereochemical course of the enzyme-mediated reductions of a wide collection of substrates belonging to well-defined chemical classes. The results of this research have allowed us to draw conclusions on the relationship between the structural characteristics of the substrate and the binding mode it adopts in the enzyme active site. The collected data can be exploited to create an empirical model to rationalise and predict the stereoselectivity of old yellow enzyme (OYE)-catalysed reductions.
Keywords: biocatalysis; ene reductase; hydrogen-2; reaction mechanisms; stable isotope tracer techniques; stereochemistry.