Racemisation in asymmetric synthesis.: Dynamic kinetic resolution and related processes in enzyme and metal catalysis

Dynamic kinetic resolution (DKR) has recently become not only an alternative to the traditional kinetic resolution, but also a new procedure for asymmetric synthesis. Enzymes are usually the tools to effect this methodology (DKR), although new techniques have emerged through the use of asymmetric transition metal catalysis. All of these methods need two supplementary steps: racemisation together with a consecutive asymmetric transformation. A breakthrough in this area appeared with the powerful combination of enzymatic resolution and transition metal-catalysed racemisation. Thus, new procedures for efficient dynamic kinetic resolution became available. This review covers the concept of dynamic kinetic resolutions emphasizing the most representative examples as well as new developments in this area. Special effort has been made to show the importance of the racemisation step in the whole asymmetric transformation process.