Aldol Reaction – Biological and Biomimetic

Abstract

In order to develop new methodology for stereospecific and catalytic aldol reactions, synthetic organic chemists are now exploring the utility of biological catalysts. There has been significant progress in this field and several efficient, selective, and predictable biological catalysts are now available for the asymmetric aldol reaction. Critical to metabolism, the aldolases catalyze in vivo aldol reactions with high chemo‐, regio‐, diastereo‐, and enantioselectivity. These enzymes are divided into four distinct areas: DHAP‐dependent, pyruvate/phosphoenol pyruvate‐dependent, acetaldehyde‐dependent, and glycine‐dependent aldolases based upon their donor dependence. Catalytic antibodies that operate via a mechanism reminiscent of a type I aldolase also have been developed. These antibodies have remarkable rate accelerations and broader substrate specificity compared to naturally occurring aldolases. However, both aldolases and catalytic antibodies share a common feature critical to their success as synthetically useful catalysts—both are capable of tolerating substrates with unprotected functional groups in aqueous solutions and give readily predictable products. This article will focus on the development of these two areas of biological aldol catalysts and discuss relevant examples as appropriate.