Method of preparing optically active alcohols which consist substantially or entirely of one enantiomer

A method of preparing optically active alcohols which consist substantially (at least 75% enantiomeric excess) or entirely of one enantiomer of formula (4) ##STR9## wherein R is phenyl, 1,2,5,6-tetrahydrophenyl, furan or benzodioxole, said R groups being substituted with one or more groups X, wherein X is a hydroxy, alkoxy(1-5 C), alkyl(1-5 C)carbonyloxy, amino, alkyl(1-5 C)carbonylamino, alkyl(1-5 C)sulphonyl, nitro, alkyl(1-5 C)suphonylamino, alkyl(1-5 C)carbonyl, halogen, cyano, alkyl(1-5 C)or cycloalkyl(5-12 C),or wherein R is a saturated or unsaturated straight or branched alkyl group having up to 30 C-atoms which may optionally be substituted with halogen, alkoxy(1-5 C), alkylthio(1-5 C),phenyl or phenoxy which may optionally be substituted with one or more groups X, and

• A is selected from the group consisting of --CH.sub.2 NH.sub.2, --CHR.sub.1 --NH.sub.2 and --CO--R.sub.1, wherein R.sub.1 is alkyl (1-8 C), alkenyl(up to 8 C), phenyl or aralkyl(up to 10 C),
• comprising
• a) protecting the hydroxyl group of an optically active cyanohydrin of formula (1) ##STR10## by reacting with a suitable base giving an optically active protected cyanohydrin of formula (2) ##STR11## wherein B is a group protecting the hydroxy group which is a radical of the formula --Si--R.sub.1 R.sub.2 R.sub.3, R.sub.1 being as defined above, R.sub.2 and R.sub.3 independently of each other being alkyl(1-8 C), alkenyl (up to 8 C), phenyl or aralkyl(up to 10 C);
• b) reacting the nitrile group of the protected cyanohydrin of formula (2) with a suitable base reagent giving an optically active compound of formula (3) ##STR12## c) removing the protecting group B.