Microbiological reduction of ethyl benxoylscetate by bakers' yeast (Saccharomyces cerevisiae), Beauwria sul@rescens or Geofrichum candidum afforded ethyl (S)-3-hydroxy-3-pheuylpropionate in high optical yield 'this enantiomerically pure alcohol was converted into both onsntiomers of fluoxetine (7). ?he product resulting from the bskers' yeast reduction had ee values (87-93%) lower than the 100% value erroneously attributed in earlier studies.
' Range using different brands and experimental conditions. ' Conditions A: substrate was added immediately after filtration and washing of the mycelium. ' Conditions B: substrate was added after a 24 h preincubation period.
Reduction of 1 with the fungus Beauveriu sul'escens gave the same enantiomer (S)-2 in 72% chemical yield and 96% ee. The reduction with Georrichum candidum was performed under two different sets of experimental conditions recently suggested by Buisson et al." In the first set (conditions A), the substrate. was directly added after filtration, washing and resuspension of the mycelium in water. In the second set (conditions B), the mycelium was separated and then preincubated during 24 h before the substrate was added This microorganism gave also the same enantiomer (S)-2 in good yield (-65%) and very high optical purity. The preincubation of the mycelium increased the selectivity of reduction and the R enantiomer is not detected by '?J NMR analysis of the Mosher derivative (Fig. 1). The specific rotation ([c@ -51.0 (c 1.5.CHC13)) of