Glutamyl-substituted amino acids

Substituted oxazolidin-5-one derivatives, which are prepared from N -protected a-annino dicarboxyhc acids and paraformaldehyde, are employed for dual protection of the a-annino and a-carboxy groups in the synthesis of P-aspartyl and y-glutamyl esters (Scheme 4).Py For this purpose the oxazolidinone derivatives are synthesized by treatment of the Z amino acids with paraformaldehyde in a nnixture of acetic anhydride, acetic acid, and traces of thionyl chloride or by azeotropic distillation of the Z amino acids with paraformaldehyde and 4-toluenesulfonic acid in benzene. The resulting heterocychc compounds are readily converted into the tert-butyl esters with isobutene under acid catalysis. Esterification is achieved with tert-butyl bromidet or with Boc-F.P l Finally, the oxazolidinone ring is opened by alkaline hydrolysis or catalytic hydrogenolysis to yield the tert-butyl esters. 

The human health aspects of this substitution are unclear, but V. sativa is known to produce the neurotoxic amino acids p-cyanoalaninc and y-glutamyl-P-cyanoalanine (Ressler, 1962 Ressler et al., 1969), the favism factors vicine and... 

GSH enables the transport of amino acids and low-molecular-weight peptides through cell membranes by transfer of y-L-glutamyl residues to amino acids and certain dipeptides [catalyzed by y-glutamyl transpeptidase (y-glutamyl transferase, abbreviation y-GT, EC 2.3.2,2)]. The detoxification of electrophilic xenobi-otic substances by elimination as - mostly water-soluble, non-toxic - 5-substituted acetylcysteine derivatives (so-called mercapturic acids) is initiated by glutathione S-transferases (abbreviation GST, EC 2.5.1.18). For further information on the biochemistry, see Lit.. ... 

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