(E)-selective hydrolysis of (E,Z)-α,β-unsaturated nitriles by the recombinant nitrilase AtNIT1 from Arabidopsis thaliana

From stereoisomeric alpha,beta -unsaturated nitriles (E,Z)-1, the recombinant nitrilase AtNlTl from Arabidopsis thaliana hydrolyses the (E)-isomers exclusively to the corresponding (E)-carboxylic acids (E)-2 with high specificity. The (E)-selectivity can also be utilised for the preparation of the isomerically pure nitriles (Z)-1, From (E,Z)-2-hydroxycinnamonitrile (E,Z)-3, the otherwise difficult obtainable (Z)-3 was prepared in 66% isolated yield. With beta,gamma -unsaturated (E,Z)-3-heptenenitrile (E,Z)-4. however, (E)-selectivity was not observed. AtNlTl exhibits not only diastereoselectivity but also regioselectivity. From a mixture of the four isomers A-D of 3-(2-cyanocyclohex-3-enyl)propenenitrile 6, exclusively isomer D ((E)-cis-6) was hydrolysed to 3-(2-cyanocyclohex-3-enyl)propenoic acid (E)-cis-7. as stated by X-ray crystal structure. Only after complete conversion of D and high enzyme concentrations, isomer C ((E)-trans-6) was hydrolysed to a small extent. (C) 2001 Elsevier Science Ltd. All rights reserved.