Combination strategy using pure enzymes and whole cells as biocatalysts for the preparation of 2-hydroxyesters and lactones from 2-oxoglutaric acid
摘要:
An innovative combination strategy that uses pure enzymes and whole microbial cells in the same process was used to prepare enantionterically pure 3-carboxyalkyl-gamma-butyrolactones and several alkyl esters of 2-hydroxyglutarates from 2-oxoglutaric acid. The method involves two consecutive biocatalytic steps. The first step, which converts the 2-oxoglutaric acid into the corresponding dialkyl esters, was catalyzed by a lipase. Then in the second step, by microbial reduction of the dialkyl-2-oxoglutarates, it is possible to obtain 3-carboxyalkyl-gamma-butyrolactones or 2-hydroxyesters depending on the length of the chain in the alkyl moiety of the esters and on the fresh or lyophilized status of the cells. (C) 2004 Elsevier Ltd. All rights reserved.
Asymmetric synthesis of alkyl 5-oxotetrahydrofuran-2-carboxylates by enantioselective hydrogenation of dialkyl 2-oxoglutarates over cinchona modified Pt/Al2O3 catalysts
The first direct asymmetric synthesis of chiral alkyl
5-oxo-tetrahydrofuran-2-carboxylates (up to 96% ee), which are important
building blocks in the synthesis of natural products by heterogeneous
cinchona-modified Pt-catalyzed hydrogenation of α-ketoglutaric acid
esters and subsequent cyclization of hydroxy esters is described.
Enantiomerically pure tetrahydro-5-oxo-2-furancarboxylic esters can be prepared either by enzymatic resolution of the racemic gamma-lactones themselves or by bioreduction with baker's yeast of dialkyl 2-oxoglutarates and subsequent cyclization of the resulting dialkyl 2-hydroxyglutarates. The best results were obtained by the former route, by which the desired compounds were isolated in high enantiomeric excess. Bioreductions were less satisfactory. In fact the hydroxyester intermediates were initially formed as racemic mixtures and their final enantiomeric enrichment was reached by asymmetric destruction, occurring in the bioreaction medium, however at the same time large amounts of alkyl 4-hydroxybutanoates were formed as side products. (C) 1999 Elsevier Science Ltd. All rights reserved.
Biotechnological Properties of Sponges from Northeast Brazil: Cliona varians as a Biocatalyst for Enantioselective Reduction of Carbonyl Compounds
To research the potential ability of whole marine sponges to act as biocatalysts, this paper describes for the first time the employment of whole Cliona varians sponge in the stereoselective reduction of prochiral alpha-keto esters and isatin to the corresponding chiral alcohols. The addition of D-fructose, D-glucose or sucrose remarkably increased the conversion ratios and stereoselectivities by this marine sponge. Furthermore, in the presence of D-glucose and D-maltose. the reduction of isatin by C. varians afforded the corresponding 3-hydroxyindolin-2-one with high conversions (85-90%) and good enantioselectivities (60-74%). These results showed that the marine sponge presents great potential to be used as biocatalyst for stereoselective reduction of carbonyl compounds.