Candida antarctica lipase catalyzes the selective monoammonolysis and aminolysis of dimethyl succinate with ammonia and aliphatic amines, respectively, in dioxane as solvent. This enzyme shows a high enatioselectivity when racemic amines are used. Optically active amidoesters are also obtained in the reaction of dimethyl succinate with racemic α-methylakylamines in hexane as solvent. In this medium, the enzyme catalyzes the formation of N-alkylsuccinimides or optically activeN -alkyl-α-methylsuccinimides from dimethyl succinate or α-methylsuccinate and amines.