Structure of the dimeric -keto acid analogue of asparagine.

Studies on the dimer of o-ketosuccinamic acid indicate that its structure is 4,6-dihydroxy-2-oxo-piperidine&carboxamide-4,6-dicarboxylic acid. The dimer was converted in acid solution to 2-hydroxy-pyridine-4,6-dicarboxylic acid; ultraviolet spectral evidence was obtained for intermediates in this transformation and studies with L-[4J4C]asparagine conmrned the pathway. On hydrogenation the dimer gave 4hydroxy-2-oxo-piperidine-5 -carboxamide-4,6-dicarboxylate. The proposed structure of the dimer is in accord with these transformations and is consistent with earlier data on the chemical and enzymatic properties of this compound.