Abstract: Addition compounds have the formula ##STR1## wherein R.sub.1 represents an aliphatic oxycarbonyl group, benzyloxycarbonyl group which can have nuclear substituents or benzoyl, aromatic sulfonyl or aromatic sulfinyl group; R.sub.2 represents methyl, isopropyl, isobutyl, isoamyl or benzyl group; R.sub.3 represents a lower alkoxyl, benzyloxy or benzhydryloxy group and n represents 1 or 2.The addition compounds are produced by reacting an N-substituted monoaminodicarboxylic acid having the formula ##STR2## with an amino carboxlic acid ester having the formula in an aqueous medium in the presence of a protease and reacting the resulting dipeptide ester with the amino carboxylic acid ester and separating the addition compound.The addition compounds can be decomposed into the constituent dipeptide esters and amino acid esters by the action of an acid.

Abstract: An improvement in a method for manufacturing dipeptides from an N-substituted aspartic acid and a phenylalanine lower alkyl ester. The two starting materials are allowed to react with each other in the presence of an immobilized metallo-proteinase in an organic solvent immiscible with water. The enzyme can be recovered for reuse thereof. The loss of materials due to the hydrolysis of the phenylalanine lower alkyl ester is reduced, so that use of the phenylalanine lower alkyl ester in a nearly stoichiometric quantity suffices for the reaction to ensure an improved yield and reduction in cost of industrial production.

Abstract: Addition compounds having the formula ##STR1## wherein R.sub.1 represents an aliphatic oxycarbonyl group, benzyloxycarbonyl group which can have nuclear substituents, or benzoyl, aromatic sulfonyl or aromatic sulfinyl group; R.sub.2 represents methyl, isopropyl, isobutyl, isoamyl or benzyl group; R.sub.3 represents a lower alkoxyl, benzyloxy or benzhydryloxy group and n represents 1 or 2 are produced by reacting an N-substituted monoaminodicarboxylic acid having the formula ##STR2## with an amino carboxylic acid ester having the formula ##STR3## in the presence of a protease.

Abstract: Addition compounds having the formula ##STR1## wherein R.sub.1 represents an aliphatic oxycarbonyl group, benzyloxycarbonyl group which can have nuclear substituents, or benzoyl, aromatic sulfonyl or aromatic sulfinyl group; R.sub.2 represents methyl, isopropyl, isobutyl, isoamyl or benzyl group; R.sub.3 represents a lower alkoxyl, benzyloxy or benzhydryloxy group and n represents 1 or 2 together with methods for preparing (I) and for decomposing (I) into the constituent dipeptide esters and amino acid esters.