Synthesis and metabolism of some substances related to δ-aminolaevulic acid

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Abstract
The diethyl ester and the ([alpha]) mono-ethyl ([delta]) hydrogen ester of [alpha] -amino-[beta]-oxoadipic acid hydrochloride were synthesized and the 2 ethyl methyl esters were prepared and identified. N-Benzyloxy-carbonyl derivatives of certain of these compounds were prepared. The hydrolysis of esters of aminooxoadipic acid, or of the corresponding N-benzyloxycarbonyl derivatives, was studied. It was not possible to isolate the free amino acid. Under acid conditions the half-ester and aminolaevulic acid were the main products, under alkaline conditions aminolaevulic acid and glycine, or their N-acyl derivatives, [delta] -Benzyloxy-carbamidolaevulic acid, also prepared from aminolaevulic acid hydro-chloride, occurs in 2 crystalline modifications. [delta] -Acetamidolaevulic acid was synthesized from aminolaevulic acid and also prepared by reductive acetylation of [delta] -oximinolaevulic acid. In contrast to simple unbranched N-acyl derivatives of glycine, N-[beta]-carboxypropionyl- and N-succinyl-glycine are hydrolyzed in vivo only to a negligible extent. Corresponding derivatives of aminolaevulic acid are not hydrolyzed, nor is the N-acetyl amino acid. Rapid excretion of the latter may account for the failure of hydrolytic systems to yield the free amino acid. Both the diester and the ([alpha]) mono-ethyl ester of amino-oxoadipic acid give rise to porphobilinogen or porphyrins in biological systems (rats liver homogenates, and suspensions or cell-free extracts of Rhodopseudomonas spheroides). This does not adequately establish amino-oxoadipic acid as the biological precursor of aminolaevulic acid.
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