Dimethyloxalacetic acid

The most interesting catalytic data available are those of Rund et al. (608, 609) on the catalyzed decarboxylation of dimethyloxalacetic acid. Phenanthroline enhances Mn(II) and Ni(II), but not Zn(II) and Mg(II) catalysis, while ligand substituents appear to alter the ratedetermining step. The catalytic process suggested is... 

The decarboxylation of the j3-keto acids oxalosuccinate and oxal-acetate catalyzed either by appropriate enzymes or by polyvalent cations can be measured spectrophotometrically by the appearance of absorption bands at higher wavelengths than those characteristic of the substrates alone. i These transient bands were once thought to represent complexes of metal with the enol form of the substrate. Studies with model compounds by Steinberger and Westheimer showed, however, that a compound that cannot form an enol, j3, 3-dimethyloxalacetate, is also decarboxylated by metals to form a transient product that has an increased ultraviolet absorption. They identified the absorbing material with the enol of the product. The mechanism of 8-keto acid decarboxylation is therefore as shown in (XI). 

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