Amino Acids and gamma-Glutamyl Derivatives in Seeds of Lunaria annua L. Part III.

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Abstract
In continuation of studies on the contents of ninhydrin-reacting constituents in unhydrolyzed seed extracts of Lunaria annua L., N5-(2-hydroxyethyl)-L-glutamine and 2-amino-4,5-dihydroxypenta-noic acid, not previously found in nature, has been isolated and identified by comparison with synthetic samples. The synthetic sample of 2-amino-4,5-dihydroxypentanoic acid was a mixture of two diastereoisomeric compounds. The configuration at C2 in the natural compound has been established as L (or S) by transformation to L-aspartic acid, whereas the configuration at C4 in unknown. In the isolation of the 2 compounds resort has been taken to untraditional principles for preparative ion-exchange chromatography using elution with volatile bases corresponding to acids with the same pK-values as those of the amino acids determining the elution order. In this way the capacity of the separation has been increased. The chemical syntheses of N5-(2-hydroxyethyl)-L-glutamine, N5-(2-methylthioethyl)-L-glutamine, N5-(2-methylsulphinylethyl)-L-glutamine, N5-(3-methylthiopropyl)-L-glutamine, N5-(3-methylsulphinylpropyl)-L-glutamine and N,N[image]-bis-(y-L-glutamyl)cystamine and of N-methylpyrazole by conventional methods are described and Rp_ values in paper chromatography for the compounds are recorded. Paper chromatographic determination of the contents of free amino acids in other parts of Lunaria annua L. has demonstrated that only very few of the many non-protein amino acids present in seeds also occur in other parts of the plant.