Approach to (R)- and (S)-ketone cyanohydrins using almond and apple meal as the source of (R)-oxynitrilase

The synthesis of aliphatic and aromatic (R)-ketone cyanohydrins through the addition of hydrogen cyanide to the corresponding ketones and the synthesis of the (S)-enantiomers through the kinetic resolution of racemic ketone cyanohydrins has been studied in the presence of almond or apple meal. Substrate tolerance of the (R)-oxynitrilases towards ketones ((RRC)-R-1-C-2=O) is highly restricted compared to that of structurally similar aldehydes, reactivity following the order of H>Me much greater than Et for R-2. In the case of aromatic methyl ketones reactivity difference (C6H5 much greater than p-Me-C6H4 for R-1) is notable. (C) 1997 Elsevier Science Ltd.