Process for preparing optically active 6-t-butoxy-3,5-dihydroxyhexanoic esters.

摘要

An optically active 6-t-butoxy-3,5-dihydroxyhexanoic ester represented by the formula: <CHEM> wherein t-Bu represents a t-butyl group; and R represents a (C1-4) alkyl group, is prepared by asymmetrically hydrogenating a 4-t-butoxyacetoacetic ester in an alcohol as solvent in the presence of a ruthenium-optically active tertiary phosphine complex of specified formula to obtain an optically active 4-t-butoxy-3-hydroxy-butanoic ester, reacting the ester in an alcohol as solvent with a lithium enolate of an acetic ester to obtain an optically active 6-t-butoxy-5-hydroxy-3-oxohexanoic ester, and asymmetrically hydrogenating the resulting ester in the presence of a diruthenium-tetrachloro optically active phosphine complex of specified formula as a catalyst. The desired product can be obtained in good yield at high stereoselectivity and is useful as a precursor of a lactone moiety of compactin, mevinolin or analogues thereof.