Chiral silicon groups as auxiliaries for enantioselective synthesis: Access to optically active silanes by biotransformation and the enantiospecific preparation of (R)-(+)-1-phenylethanol

The synthesis of the optically active alkoxymethyl-substituted acetylsilanes (+)-3 and (-)-3 was achieved by the bioreduction of (+/-)-3 with resting cells of Trigonopsis variabilis to the diastereoisomeric alcohols (+)-4- and (+)-5. These two compounds were separated by chromatography and separately reoxidized to the desired optically active silyl ketones. As a simple example of the use of chiral alkoxymethyl-substituted silyl groups as auxiliaries for the synthesis of enantiomerically enriched silicon-free compounds, the chelate controlled 1,2-addition of phenyl lithium to (-)-3 and the stereospecific conversion of the corresponding major addition product to (R)-(+)-1-phenylethanol (+)-10 is presented.