Synthesis of optically active 4,5-dihydroisoxazolecarboxylic acids

A series of regioisomers of 4,5-dihydroisoxazolecarboxylates have been synthesized in the 1,3-dipolar intermolecular cycloaddition and subjected to enzymatic hydrolysis by o:-chymotrypsin from bovine pancreas ( type II) and to micro bial hydrolysis by an Aspergillus niger fungus. For some compounds this hydrolysis time led to the obtaining of a racemic mixture, and for others the reaction was enantioselective.