Process for preparing optically active cyanohydrins and secondary products

The invention relates to a process for preparing optically active cyanohydrins using a highly active (R)-hydroxynitrile lyase extract. The present invention relates to a process for preparing optically active cyanohydrins of the formula (II), by reacting an aldehyde of the formula (I) with HCN in a water-immiscible organic solvent in the presence of water, in the absence or presence of a buffer, in the presence of a (R)-hydroxynitrile lyase, where X, Y and Z in formula (II) have the same meaning as in formula (I), independently of each other are identical or different and are H, F, Cl, Br, I, OH, O(C-C-alkyl), OCOCH, NHCOCH, NOor C-C-alkyl.