Oxalacetate analogs

The stereoselective catalyzed addition of water or methanol to dimethyl acetylenedicarboxylate (DMAD) was reported to yield oxalacetic acid dimethylester or dimethyl methoxyfumarate. The catalyst precursor cis-[Pd(PMe2Ph)2(solvent)2] [BFJj was prepared from ds-[PdCl2(PMe2Ph)2] and AgBp4 (Eq. 6.54). The analogous platinum complex was not effective, however [99]. 

Following the synthesis by Comforth and his associates18 of NeuAc from oxalacetate and 2-acetamido-2-deoxy-D-mannose, Ghalambor and Heath29,31 prepared KDO (isolated as the crystalline methyl 2,4,5,7,8-penta-0-acetyl-3-deoxy-D-manno-2-octulopyranosonate, 70) from D-arabinose and oxalacetate by an analogous reaction (see Scheme 20). 

The introduction of the a-keto acid function on the way to the ulosonic acids is a main problem of their syntheses. By analogy with the biosynthetic pathway, the aldol reaction between sugar aldehydes and a pyruvate equivalents seems to be the most simple and versatile. As it has been demonstrated by Comforth [74] in the first chemical synthesis, the reaction of arabinose and oxalacetic acid as pyruvate equivalent, followed by decarboxylation afforded KDO, albeit in low yield. This condensation has been optimized by use of Ni(II) catalyst for the decarboxylation [75], In this case, reaction of D-mannose and oxalacetic acid gave KDN (11) and its D-manno epimer 37 in 70% yield [75] (Scheme 12). 

The phytopathogenic fungus, Macrophoma commelinae has the ability to transform 2-pyrone 146 into the corresponding benzoate analog macrophomate (152) (Scheme 27). This complex aromatic conversion is catalyzed by a single enzyme, with oxalacetate as a substrate for the C3-unit precursor. MPS is a... 

Sulfinylpyruvic acid accumulates as a result of the transaminating activity. It is an analog of oxalacetic acid, and like this compound, it is decomposed to pyruvate and SOs under the influence of Mn ". The reaction is analogous to the j3-decarboxylation of oxalacetate by Mn++. Mn++ also catalyzes the oxidation of SOj to S04 . As a consequence, reactions 5 and 6 of Fig. 2 are assumed to be nonenzymatic. 

Malate Inhibition (see Table 4.3). Following our initial observation that L-malate and oxalacetate, and to a lesser extent D-malate, aspartate, and glutamate inhibit maize root PEP carboxylase (see Ting, 1971), Queiroz (1967) reported that the PEP carboxylase of Kalanchoe leaves was sensitive to L-malate. Based on these data, it was proposed that L-malate could regulate its own synthesis by feedback inhibition of PEP carboxylase (Queiroz, 1967). It is possible that malate is simply a product analog, acting similarly to oxalacetate, yet in maize roots, oxalacetate and malate inhibit in a different manner (Ting, 1968 a). 

Fig. 2. Probable biosynthesis of protolichesterinic acid (1), roccellic acid (2), rangiformic acid (3), and acarenoic acid (5). The labeling given for (1) is the one expected after administration of the likely precursor oxalacetate by analogy with the results reported for succinate.

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