A number of Merrifield resin supported dipeptide and tripeptide catalysts have been developed of which Pro-Ala-O-P, catalyst A, was found to be an efficient catalyst for asymmetric direct aldol reactions. Aldehydes and ketones underwent smooth aldol reaction in the presence of a catalytic amount of A at room temperature under neat reaction conditions and generated the corresponding products with excellent isolated yields (≤98%), good diastereoselectivities (dr ≤ 90:10) and enantioselectivities (≤95% ee). In addition, catalyst A could be used seven times without loss of its catalytic activity.
Merrifield resin - organocatalyst - aldol reaction - peptide - neat reaction conditions