Abstract: A process for the preparation of disodium Z-L-aspartate from fumaric acid, in whicha) fumaric acid is reacted with ammonia in an inert diluent in the presence of aspartase or aspartase-producing microorganisms to give ammonium L-aspartate thenb) the ammonium L-aspartate-containing solution is treated with sodium hydroxide, forming, depending on the amount of sodium hydroxide used, the mono- or disodium L-aspartate or a mixture thereof, andc) the eliminated ammonia is returned to a fumaric acid suspension, which is used as starting solution for further enzymatic reactions, and thend) the residual mono and/or disodium L-aspartate-containing solution is reacted with benzyloxycarbonyl chloride at a pH of between 9 and 14, with the simultaneous addition of sodium hydroxide, to form disodium Z-L-aspartate.

Abstract: The invention relates to a process for the preparation of an oligopeptide or amino acid alkyl ester.HCl salt, the alkyl group being methyl, ethyl, isopropyl or n-propyl, by converting an oligopeptide.HCl salt or amino acid.HCl salt with an alkanol corresponding to the alkyl group under the influence of an acid catalyst, 0.01-0.5 mol HCl relative to the oligopeptide.HCl salt or amino acid.HCl salt in combination with an acid ion exchange resin being used as acid catalyst.