Glutamic Acid-l-semialdehyde, a Hypothetical Intermediate in the Biosynthesis of 5-Aminolevulinic Acid

W hether glutamate-l-sem ialdehyde (G -l-SA ) or 4,5 dioxovalerate (DOVA) is the intermedi­ ate between glutamate and A LA in the C-5 tetrapyrrol pathway is still a matter of controversy. Since no data characterizing G -l-SA are available it is not possible either to identify G -l-SA as intermediate or a precursor of ALA. Therefore, attem pts were made to establish a chemical synthesis of this compound. Two strategies were developed: starting from protected glutamate via an open chain mechanism or from the cyclic compound pyroglutamic acid or derivatives. None of the attempts were successful. Both approaches yielded undefined polymeric products when it was tried to liberate G -l-SA from the last interm ediate of the synthesis sequence.