Highly diastereo- and enantioselective direct aldol reaction catalyzed by simple amphiphilic proline derivatives

Two novel amphiphilic L-proline derivatives bearing long alkyl chain on the 4-position via ether bonds, 1a and 1b, have been synthesized and evaluated for the asymmetric direct aldol reaction in organic solvents as well as in water. The catalytic activities with 5 mol% of 1a are better than that of 30 mol% of proline itself being used. Especially, high yields (up to 99%), excellent enantioselectivities (up to 99% ee) and anti-diastereoselectivities (up to 99:1) are achieved in the reactions of aromatic aldehydes and cyclic ketones at room temperature with 5 mol% of 1a in water.