L-Prolinecatalyzes the aldol addition reaction of acetone to β-substituted α-ketoesters with dynamickineticresolution, providing the desired adduct in good yield with excellent diastereoselectivity (up to >99:1 dr) and enantioselectivity (up to 98% ee). The absolute configuration of the chiral adduct was assigned by single-crystal X-ray diffraction analysis. A tentative explanation of the stereochemical