Industrial Biotransformations

OH
O
R OR'
R = alkyl, aryl
lipase
Ru-catalysts
3.17 Cyanohydrins, Hemithioacetals and Hemiaminals
OAc
O
R OR'
3.17
Cyanohydrins, Hemithioacetals and Hemiaminals
HO
R
CN
R'
oxynitrilase
O
R R'
+
+
OH
O
R OR'
Many (R)- or (S)-selective hydroxynitrile lyases (formerly also denoted as “oxynitrilases”)
are available for the synthesis of cyanohydrins, which can then be converted into a
variety of synthetically useful chiral intermediates [52].
Racemic cyanohydrins can be converted into one enantiomer with high optical purity
in a dynamic resolution fashion due to the intrinsic instability of the respective molecule.
The same principle can also be applied to hemithioacetals [53] and N-acyl hemiaminals
[54].
OH
R CN
OH
R SR'
OH
NR
O
lipase
acyl donor
lipase
acyl donor
lipase
acyl donor
R, R' = organic substituents
OAc
R CN
OAc
R SR'
OAc
NR
O
+
+
+
CN -
OH
R CN
OH
R SR'
OH
NR
O
81