PREPARATION OF ENANTIOMERICALLY PURE (R)-(1-HYDROXYETHYL)DIMETHYL(PHENYL)SILANE USING RESTING CELLS OF SACCHAROMYCES-CEREVISIAE (DHW S-3) AS BIOCATALYST

The prochiral sila-ketone acetyldimethyl-(phenyl)silane (1) was reduce d enantioselectively into (R)-(1-hydroxyethyl) dimethyl(phenyl)silane [(R)-2] using resting cells of the commercially available yeast Saccha romyces cerevisiae (DHW S-3) as the biocatalyst. The bioconversion was performed on a 2.0-g scale in a 5-1 bioreactor. Starting with a subst rate (1) concentration of 0.4 g.1(-1), the highest production rate mea sured for this bioconversion was about 45-55 mu mol (R)2.1(-1)min(-1). After an incubation time of 1 h, all substrate in the medium had been converted, either biocatalytically reduced to (R)-2 or (probably chem ically) converted into dimethyl(phenyl)silanol (Me(2)PhSiOH). After ex traction of the cell-free medium with ethyl acetate/dichloromethane an d subsequent purification of the extract by Kugelrohr distillation and chromatography on silica gel (medium-pressure liquid chromatography), 800 mg (yield 40%) of the bioconversion product (R)-2 was isolated. A s shown by HPLC studies (cellulose triacetate as the chiral stationary phase) and H-1-nuclear magnetic resonance experiments (after derivati zation of the bioconversion product with a chiral auxiliary agent), co mpound (R)-2 was almost enantiomerically pure (> 99% enantiomeric exce ss).