High Quality Content by WIKIPEDIA articles! The Hajos–Parrish–Eder–Sauer–Wiechert reaction in organic chemistry is a proline catalysed asymmetric Aldol reaction. The reaction is named after its principal investigators from Hoffmann-La Roche and Schering AG. Discovered in the 1970s the original Hajos-Parrish catalytic procedure - shown in the reaction equation - leading to the optically active bicyclic ketol as well as the Eder-Sauer-Wiechert modification leading to the optically active enedione through the loss of water from the ketol paved the way of asymmetric organocatalysis. It has been used extensively as a tool in the synthesis of steroids and other enantiomerically pure molecules.