Abstract: Process is described for the production of L-amino acids of general formula I ##STR1## in which R.sub.1 means an alkyl radical with at most 12 carbon atoms optionally substituted by hydroxy groups, mercapto groups, halogen atoms, amino groups, carbonyl groups or guanidino groups and/or interrupted by oxygen atoms, nitrogen atoms or sulfur atoms, and in the case of mercapto compounds of formula I also their dithio compounds, characterized in that the microorganism Nocardia spec. DSM 3306 or its enzymes are allowed to act on a D,L-imidazolidinedione derivative of general formula II ##STR2## in which R.sub.1 has the above-named meaning or, in the case of mercapto compounds of formula II, also in their dithio compounds.

Abstract: A process is described for the preparation of aspartic acid 4-(phenylmethyl) ester from aspartic acid and benzyl alcohol, characterized by utilizing a reaction mixture which contains, per mole of aspartic acid, 10-40 moles of benzyl alcohol and 1-5 moles of acetyl chloride, by conducting the reaction at a temperature of -10.degree. C. to 50.degree. C., and by separating the product of the process, after reaction has taken place, by neutralization with organic bases.