Process for the preparation of derivatives of 3,5-dihydroxypentanoic acid

Process for the selective preparation of syn derivatives of 3,5-dihydroxypentanoic acid of general formula:

• ##STR7## in which Z represents an alkoxy radical in which the alkyl part contains 1 to about 4 carbon atoms, an alkylthio radical in which the alkyl part contains 1 to about 4 carbon atoms, an amino radical, an alkylamino radical in which the alkyl part contains 1 to about 4 carbon atoms or a dialkylamino radical in which each alkyl part contains 1 to about 4 carbon atoms,
• R represents either a radical R.sub.1 -Y- in which Y represents a --CH.sub.2 CH.sub.2 --, --CH.dbd.CH-- or --C.tbd.C-- radical and R.sub.1 represents an optionally substituted aliphatic, alicyclic, aromatic or heteroaromatic radical or a radical ##STR8## in which R.sub.2 represents a halogen atom or an alkoxy radical in which the alkyl part cotains 1 to about 4 carbon atoms, an alkylthio radical in which the alkyl part contains 1 to about 4 carbon atoms, an arylthio radical, an amino radical, a monoalkylamino radical in which the alkyl part contains 1 to about 4 carbon atoms or a dialkylamino radical in which each alkyl part contains 1 to about 4 carbon atoms and R.sub.3 represents a hydrogen atoms or is identical to R.sub.2, characterized in that a chiral or racemic hydroxyketone or general formula:
• ##STR9## in which R and Z are defined as above, is stereoselectively reduced using sodium or potassium borohydride or cyanoborohydride in combination with a titanium derivative, and the produce obtained is isolated.