Process for the preparation of substituted diaminodicarboxylic acid derivatives

The prepn. of substd. diaminodicarboxylic acid derivs. of formula (I) by opt. mixed Kolbe synthesis comprises dissolving a protected amino acid derv. of formula (II) with a protected amino acid derv. of formula(III) in a solvent R OH or in a heterocyclic or in a heterocyclic or aliphatic solvent contg. ≥ 1 hetero atom, or in an mixt. of such solvents, subjecting the soln. to electrolysis with Pt gauze electrodes and then opt. hydrolysing the prod. with LiOH. R and R = each opt. halogenated, linear, branched or cyclic 1-10C alkyl or COA or COOA; A = opt. halogenated, linear, branched or cyclic 1-10C alkyl, benzyl (opt. mono- or poly-substd. with halogen, NO2, alkoxy, and/or CN) or 9-fluorenylmethyl; R = linear or branched 1-4C alkyl; the centres of chirality in (I) are determined by the educts used and are both L or both D or are D, L or L, D; n = 2-8; k and l are integers, such that k+l = n; R = R .