Comparative study in the asymmetric bioreduction of ketones by plant organs and undifferentiated cells

Stereoselective reduction of prochiral ketones was studied by using both cell cultures and wild tissues of various endemic plant species. Dedifferentiated cell cultures of Baccharis crispa reduced regioselectively, with excellent stereocontrol, and in an anti-Prelog manner the methyl ketone moiety of a diketone, meanwhile Tessaria absinthioides cell cultures yielded the other antipode of the secondary alcohol with an optical purity higher than 98% ee. Therefore, it is possible to prepare the S and R isomers of a secondary alcohol by reduction of the corresponding prochiral ketone with these two biocatalysts. Moreover, significant differences in the reductive capacity of cell cultures and differentiated tissues of the same plant species were found. This fact allows improving the yields and optical purities and, even more interesting, obtaining the antipode of a secondary alcohol with the same plant species by using alternatively both biocatalytic systems. (c) 2007 Elsevier B.V. All rights reserved.