Abstract: An optically active catalyst containing a salen ligand of formula (II) and vanadium at oxidation stage (IV), wherein the groups R, R′ and R″ of the salen ligand independently of one another represent hydrogen, branched or unbranched C1-C10 alkyl groups or an O(C1-C4-alkyl) group or F, Cl, Br or I, an optionally substituted aryl group, or —(CH2)m— whereby m represents a whole number ranging between 1 and 8 and the catalyst contains between 1.4 and 10 equivalents of a salen ligand for an equivalent of vanadium (IV).

Abstract: The invention relates to a method for producing optically active cyanohydrins and the corresponding &agr;-hydroxy-carboxylic acids, starting from an aldehyde, hydrogen cyanide and an optically active vanadyl-salen catalyst, whereby the reaction mixture is reacted at a temperature of between 0 and 60° C. Between 0.8 and 10 equivalents of hydrogen cyanide and between 0.0001 and 0.05 equivalents of vanadyl-salen catalyst in relation to the aldehyde, (concentration of between 0.5 and 4 mol/litre solvent), are preferably used. After said reaction the optically active cyanohydrin or after an acid hydrolysis the corresponding optically active &agr;-hydroxycarboxylic acid can be isolated with a surplus of enantiomers. The vanadium catalyst used in the invention contains a salen ligand, whereby the ratio salen ligand: vanadium (IV) in the catalyst ranges between 1.4:1 and 10:1.