SELECTIVITY IN ENZYME CATALYZED REACTION - PREFERENTIAL HYDROLYSIS OF SATURATED METHYL-ESTER OVER THE CORRESPONDING UNSATURATED ESTER BY PIG-LIVER ESTERASE

Saturated methyl ester is preferentially hydrolysed in presence of corresponding is-proportional-to,beta-unsaturated ester by Pig Liver Esterasse. This selectivity is known for aliphatic, aromatic and heterocyclic esters. Chemo, regio and stereoselective transformations are an important goal towards synthetic efficiency (Bartman and Trost, 1984). Among the various methods that are employed to achieve such reactions, enzymatic transformations are in the forefront of current research activities (Jones, 1986) because of several advantages over the chemical methods. These include extremely high degree of selectivity, easier isolation of products, specially with immobilized enzymes and their reusability. In the past decade this class of biocatalysts has provided a plathora of valuable selective transformations (Boland et.al, 1991). Pig Liver Esterase (PLF) is one such enzyme which has been thoroughly studied and used for asymmetric (Zhu and Tedford, 1990) and regioselective (Adachi et-al, 1986) hydrolysis of esters. Several chiral building blocks for the synthesis of complex natural products (Imori et.al., 1983) have been synthesized through PLE. In this communication, we report the preferential hydrolysis of a saturated ester over its unsaturated counterpart. The preference is total and works well for aliphatic, aromatic as well as heterocyclic systems.