Highly Efficient Direct Asymmetric Aldol Reactions Catalyzed by a Prolinethioamide Derivative in Aqueous Media

L-Prolinethioamide derivative 1c, prepared from the readily available natural amino acids L-proline and L-valine, was studied for the direct asymmetric aldol reaction of acetone with various aromatic aldehydes at 0 degrees C or room temperature. A loading of only 0.1-0.2 mol-% of derivative 1c was employed in this catalytic system, and excellent enantio-selectivities and yields (up to 98% yield, >99 % ee) could be achieved in aqueous media.