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

Abstract

The synthesis of the optically active alkoxymethyl-substituted acetylsilanes (+)-3 and (−)-b 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.
Silane (±)-3 was reduced by Trigonopsis variabilis (DSM 70714) to (+)-4 and (+)-5, which were separated and oxidized to (R)-(−)-3 and (S)-(+)-3. (R)-(−)-3 was finally converted to (R-(+)-1-phenylethanol [(R)-(+)-12].