Stereochemistry of the baker's yeast mediated reduction of the CC bond of (Z)- and (E)-5-benzoyloxyhex-3-en-2-one

Abstract

Baker's yeast reduction of the Z and E enones 5 and 6 to the methyl ketone 7 proceeds with kinetic preference for the R and S enantiomers, respectively. However, irrespective of the double-bond stereochemistry and of the absolute configuration of the oxygen-bearing carbon atom at position 5, the CC bond reduction occurs by formal anti addition of hydrogen, with delivery of the hydrogen atom at position 4 from the re-face of the molecule, as shown by 2H NMR studies onto lactones 17 and 18 obtained in experiments with deuteriated precursors.