Water influences the enantioselectivity in the proline or prolinamide-catalyzed aldol addition of acetone to isatins

The addition of small quantities of water to the proline or prolinamide-catalyzed aldol addition of acetone to isatin can result in increased enantioselectivity. DFT B3LYP calculations with a water molecule explicitly incorporated in the aldol transition states reproduce the observed enantioselectivity.