Stereoselective reduction of ketones has classically been accomplished using boron- or heavy metal-based reagents bearing chiral ligands. Biocatalysts offer opportunities to implement greener processes that reduce solvent utilization and generate less waste. We will describe two case studies in biocatalyst development. The first is the creation of a ketoredutases for the production of TBIN, the key advanced intermediate in the synthesis of atorvastatin. The second example is the development of an optimized ketoreductase catalyzing the key stereoselective reduction in the synthetic route for montelukast.