Nitrilase-mediated Hydrolysis of Cyanohydrins

The extent of amide production varied erratically, depending on the nitrile and the biocatalyst. It was negligible in the hydrolysis of la, except when PfNLase was employed as the biocatalyst [3, 5]. The o-chloro substituent in lb caused NIT-104 and 107 to produce considerable amounts of amide. NIT-106, which acted selectively in the hydrolysis of la and lb, sluggishly mediated the hydrolysis of Ic into a nearly equimolar mixture of acid and amide. In conclusion, there is no best nitrilase with regard to acid/amide selectivity. 

The nitrilases from Biocatalytics were (R)-selective in aU cases where measurements were feasible, but not always to the same extent PfNLase, in contrast, showed little enantiomeric bias with these nitriles. It is worth noting that in a recent survey the majority of nitrilases that hydrolyzed la were biased towards the (R)-enantiomer [10]. 

From these results we concluded that the preferred biocatalysts for the selective hydrolysis of la, lb and Ic into the (R)-acids are, respectively, NIT-104, NIT-106 and NIT-104, although the hydrolysis of lb and Ic is rather less enantioselective than would be desirable. Thus, in a preparative experiment, NIT-104 converted la (0.1 M starting concentration) into (R)-mandelic acid (98% conversion, 98% ee), attesting that under the prevailing conditions the racemisation of the nitrile is fast 

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