Ruthenium-catalysed DKR

Chirality from Dynamic Kinetic Resolution By Helene Pellissier Helene Pellissier 2011 

The DKR applied to cyclic jS-ketoesters, such as 2-substituted-3-oxo carboxylic esters, revealed that the stereochemical course of the reaction was influenced by the structures of the substrates.When comparing the asymmetric hydrogenation of the five-membered ring to those obtained with cyclic 

The (2i ,3i )-hydroxy-a-methyl ester was further converted into the expected natural anticancer agent, (2i ,3i )-dolaproine. 

In 2000, Genet s group described an efficient formal synthesis of ( )-balanol, a natural produet showing remarkable inhibitory properties towards protein kinase This synthesis was based on the ruthenium-catalysed hydrogenation 

Very recently. Steward and Johnson developed the DKR of jS-silyloxy-a-keto esters, previously prepared through a cyanide-catalysed benzoin-type reaction between silyl glyoxylates and aldehydes. The asymmetric transfer hydrogenation was performed in the presence of TEA as the base, formic acid as the hydride source, and a ruthenium catalyst bearing a chiral 1,2-diamine, providing the corresponding enantioenriched monoprotected diols with moderate diastereo- and enantioselectivities of up to 66% de and 52% ee, respectively. 

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The lipase-ruthenium-catalysed DKR of other functionalised alcohols, such as diols, has been widely studied by Backvall s group in recent years." These authors have developed a highly efficient synthesis of enantiopure diacetates of the symmetric diols, 2,4-pentanediol and 2,5-hexanediol, by combining a ruthenium catalyst with lipase CAL-B in the presence of vinyl acetate or isoproprenyl acetate as the acyl donor, respectively. Excellent yields, and diastereo-and enantioseleetivities were obtained in both cases, as shown in Scheme 4.23. 

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