Regioselective biotransformation of the dinitrile compounds 2-, 3- and 4-(cyanomethyl) benzonitrile by the soil bacterium Rhodococcus rhodochrous LL100-21

The cyanomethyl benzonitrile compounds used for this study contain two cyan o groups: a -CH2CN side chain, plus a cyano group attached to the benzene r ing. The ortho, meta and para -CH2CN substituted compounds were biotransfor med using whale cell suspensions of the bacterium Rhodococcus rhodochrous L L100-21. The bacterium had previously been grown on the mono-nitrile compou nds propionitrile, benzonitrile or acetonitrile, inducing the formation of nitrile hydrolyzing enzymes. Suspensions of R. rhodochrous LL100-21 that had been grown on propionitrile or benzonitrile converted the aliphatic group of 2-(cyanomethyl) benzonitr ile (a) to the corresponding carboxylic acid, 2-(cyanophenyl) acetic acid ( d) with excellent recovery of the product and no evidence for any other pro ducts. Conversely, when grown on acetonitrile the bacterium converted 2-(cy anomethyl) benzonitrile (a) to the amide derivatives 2-(cyanophenyl) acetam ide (k) and 2-(cyanomethyl) benzamide (l) but only in low yields. Biotransformations of 3-(cyanomethyl) benzonitrile (b) and 4-(cyanomethyl) benzonitrile (c), by suspensions of bacteria that had been grown on benzoni trile or propionitrile, resulted in hydrolysis of the aromatic nitrile to p roduce 3- and 4-(cyanomethyl) benzoic acid (j) and (m), respectively, both with a high yield. Low concentrations of other products were also detected, for example the diacids 3- and 4-(carboxyphenyl) acetic acid (h) and (i). When the bacterium was grown on acetonitrile it could biotransform 3- and 4 -(cyanomethyl) benzonitrile (b) and (c) to different products indicating le ss regiospecificity by the nitrile hydratase enzyme. Comparison of the initial rates of conversion of the aliphatic cyano side c hain of 2-(cyanomethyl) benzonitrile (a) and other substituted benzonitrile s indicated that electronic effects did not affect the initial rate of the reaction as they would require transmission through an SP3 methylene carbon atom. (C) 2001 Elsevier Science Inc. All rights reserved.