Project Abstract This research program develops and applies state-of-the-art computational methods to understand stereoselectivities of enzyme catalysts for reactions of high synthetic value. The control of stereoselectivity is an essential feature of efficient synthesis, and this program provides explanations of the origins of these selectivities and builds on these to predict new enzyme catalysts for stereoselective reactions. Collaborators test these predictions. These are critical elements in the synthesis of effective pharmaceutical agents.