Trifluoromethyl vs. methyl ability to direct enantioselection in microbial reduction of carbonyl substrates.

The stereoselective reduction of 3-trifluoromethylcyclohexanone (1a), (E)-1.1.1-trifluoro-4-phenyl-3-buten-2-one (3a). and their unfluorinated analogues 1b and 3b has been performed with some growing microorganisms. Differences in the electronic and steric properties of the trifluoromethyl and methyl residues result in different chemo- and stereoselectivities in the microbial reduction of phenylbutenones 3a and 3b while cyclohexanones 1a and 1b showed strictly similar stereoselectivities. A new protocol based on C-13 NMR spectra of 2-phenylpropionic acid esters has been used to assign the absolute configuration of the obtained secondary alcohols. (C) 1998 Elsevier Science Ltd. All rights reserved.