PROCESS FOR THE PREPARATION OF CHIRAL ALPHA-HYDROXYCARBOXYLIC ACIDS

摘要

A process for the preparation of chiral a-hydroxycarboxylic acids of the formula in which R1 is a C1-C2-alkyl radical optionally substituted by halogen atoms and R2 is a C2-C3-alkyl radical optionally substituted by halogen atoms, from a compound of the formula in which R1 is as defined above, R2' is a C2-C3-alkylene radical optionally substituted by halogen atoms, m is 0 or 1 and R is an optionally substituted alkyl radical, an aryl radical, heteroaryl radical or a heterocyclyl radical and X can be oxygen, sulfur, sulfinyl, sulfonyl, imino, C1-C6-alkylimino, xanthate, silyl, or, if m is equal to 0, halogen, which is reacted in the presence of a cyanide group donor to give the corresponding (R)- or (S)-cyanohydrin or its racemate of the formula then is converted by means of acidic hydrolysis into an acid of the formula or its racemate, and by cleavage of the group of the formula (R)m-X (V), where a resolution is optionally first carried out, the desired chiral a-hydroxycarboxylic acid of the formula (f) is obtained.