Dicarbonyl reduction by single enzyme for the preparation of chiral diols

Chiral diols are a group of key building blocks useful for preparing a variety of important chiral chemicals. While the preparation of optically pure diols is generally not an easy task in synthetic organic chemistry, three classes of enzymes, namely dicarbonyl reductase, dioxygenase and epoxide hydrolase, display remarkable ability to stereoselectively introduce two hydroxyl groups in a single-step enzymatic conversion. In this tutorial review, we pay special attention to dicarbonyl reductases that directly produce chiral diols through the bio-reduction of two carbonyl groups. The dicarbonyl reductases include diketoreductase, α-acetoxy ketone reductase and sepiapterin reductase. We present these exceptional enzymes in the context of source and properties, structure and catalytic mechanism as well as biocatalytic application. In addition to the broad substrate specificity, the excellent stereoselectivity and high catalytic efficiency of these enzymes have positioned them as valuable biocatalysts. With more sophisticated understanding of the structure-function relationship, the practical utilities of these enzymes associated with their interesting chemistry will be considerably appreciated over time. Moreover, rational redesign and molecular evolution of these unusual biocatalysts will truly enable their broader applications in the synthesis of chiral diols in the future.