Chemoenzymatic dynamic kinetic resolution (DKR) via combined ruthenium and enzyme catalysis was used in the key step of a synthesis of a neonicotinoid pesticide derivative (S)-3. The DKR was carried out under mild conditions with low catalyst loading. The method gives (S)-3 in high enantiomeric excess (98%).
[Show abstract][Hide abstract] ABSTRACT: Dynamic kinetic resolution (DKR) is an attractive process for the transformation of racemic mixtures into optically active compounds. For successful DKR, efficient racemization is required while the kinetic resolution is proceeding. This Microreview mainly summarizes the recent developments in the DKR of alcohols and amines, based on metal-catalyzed racemization and enzymatic acylation in a single reaction vessel. Related reactions involving precursors of alcohols and amines such as ketones, enol acetates, and ketoximes are also described. Reaction conditions are arranged according to racemization catalysts, and substrates employed in the DKR are tabulated. Suggested mechanisms for metal-catalyzed racemizations are also summarized.
European Journal of Organic Chemistry 02/2010; 2010(6):999 - 1015. DOI:10.1002/ejoc.200900935 · 3.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dimeric palladium bromide complexes bearing monodentate N-heterocyclic carbene ligands have been identified as efficient catalysts for the chemoselective racemization of axially chiral allenyl alcohols. In combination with porcine pancreatic lipase as biocatalyst, a dynamic kinetic resolution has been developed, giving access to optically active allenes in good yield and high enantiomeric purity
Chemistry - A European Journal 03/2010; 16(15):4447-4451. DOI:10.1002/chem.201000301 · 5.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: New methods continue to be developed for the dynamic kinetic resolution (DKR) and deracemisation of racemic chiral compounds, in particular alcohols, amines and amino acids. Many of the DKR processes involve the combination of an enantioselective enzyme, often a lipase or protease, with a metal racemisation catalyst. A greater range of ruthenium-based racemisation catalysts is now available with some showing good activity for the racemisation of amines that are more difficult to epimerise than the corresponding alcohols. In terms of deracemisation processes, further improvements have been achieved with the deracemisation of alcohols, using combinations of stereocomplementary ketoreductases, and additionally transaminases have been applied to the deracemisation of racemic amines.
Current opinion in chemical biology 04/2010; 14(2):115-21. DOI:10.1016/j.cbpa.2009.11.027 · 6.81 Impact Factor
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