Synthesis of ∈-aspartyl-lysines and of isohexylamides of aspartic acid

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Abstract
[epsilon] -N-([alpha]-L-Aspartyl)-L-lysine was obtained by interaction of N-benzyloxy-carbonyl-L-aspartic anhydride with the copper complex of L-lysine. [epsilon] -N-([alpha]-Aspartyl)-L-lysine and the corresponding [beta]-aspartyl-lysine were synthesized by the mixed-anhydride method from [alpha]-toluene-p-sulfonyl-L-lysine benzyl ester and the [beta]- and [alpha]-benzyl esters respectively of N-benzyloxycarbonyl-L-aspartic acid. The [beta]-isohexylamide of L-aspartic acid was synthesized by the mixed-anhydride method from [alpha]-benzyl N-benzyloxycarbonyl-L-aspartate and isohexylamine. The [alpha]- and [beta]-isohexylamides of DL-aspartic acid were synthesized from N-isohexyl-maleamic acid. The two [epsilon] -aspartyl-lysines are readily separated by electrophoresis on paper at pH 2.3 or 9.1, but not by paper chromatography in a number of solvent systems. The two isohexylamides of aspartic acid can be separated in paper chromatograms run in butanol-acetic acid-water.