Mesaconic add

Of a similar character is the relation subsisting between the isomeric adds of this series containing five atoms of carbon, viz. itaconic add, dtraconio add, and mesaconic add. There are no less than eleven possible formulm for this five. cbon group of acids but the three individual formule belonging to the three known adds cannot at present he determined. The following four formula will serve as specimens of the whole, and as illustrations of the cause of isomerism in these adds... 

The concentration of the mother liquor must be carried out in steps in order to obtain an effident separation of mesaconic add. 

S. Except for oxido-reductases, transferases, and hydrolases, most ligases (enzymes that catalyze bond formation) are entirely substrate specific. Thus, fumarate hydratase (or fumarase) reversibly and stereospecifically adds water to fumaric acid to produce (S)-( — )-malic acid only (8) (Figure 1), and another enzyme, mesaconase, adds water to mesaconic acid to form (+ )-citramalic acid (9) (Figure 2). Although no extensive studies are available, it appears that neither fumarase nor mesaconase will add water stereospecifically to any other a,(3-unsaturated acid. 

Preparation 423.—Mesaconic Acid [tians-3-Carboxy-2-luten add], CH,... 

In the 1 H-NMR spectrum (270 MHz) the methine and the two methylene protons of methylsuccinic add gave rise to a well-resolved ABC system. In the two enantiomers 38 and 39 the H atoms HR<,R/HSlS and H5(R/HWe.v are pair-wise reflection equivalent, i.e., identical in the NMR spectrum, whereas the diastereotopic geminal protons can be distinguished by their different chemical shifts. For the assignment of the signals to the diastereotopic protons, reference compounds of known configuration were synthesized by treating mesaconic and citraconic acids (40 and 42) with deuterated diimide. The known syn-addition of deuterium [35,36] afforded the racemic but stereospecifically dideuterated methylsuccinic acids (41 and 43) (Fig. 25). 

Itaconic acid (I), which is produced commercially by fermentation, is isomeric with mesaconic acid (II) and dtraconic acid (III), and in the presence of strong base may form equilibrimn mixtures of the salts (4). Other derivatives such as the esters and the amides can be similarly isomerized (5, 6). The mesaconate seems to be the most stable isomer in polar solvents in the temperature range — 78° to 100° C or higher. The well known conversion of itaconic to citraconic add by heating above the melting point probably jjroceeds throu itaconic anhydride. 

Methylsuccinic acid has been prepared by the pyrolysis of tartaric acid from 1,2-dibromopropane or aHyl halides by the action of potassium cyanide followed by hydrolysis by reduction of itaconic, citraconic, and mesaconic acids by hydrolysis of ketovalerolactonecarboxylic acid by decarboxylation of 1,1,2-propanetricarboxylic acid by oxidation of /S-methylcyclo-hexanone by fusion of gamboge with alkali by hydrog nation and condensation of sodium lactate over nickel oxide from acetoacetic ester by successive alkylation with a methyl halide and a monohaloacetic ester by hydrolysis of a-methyl-a -oxalosucdnic ester or a-methyl-a -acetosuccinic ester by action of hot, concentrated potassium hydroxide upon methyl-sucdnaldehyde dioxime from the ammonium salt of a-methyl-butyric add by oxidation with. hydrogen peroxide from P-methyllevulinic add by oxidation with dilute nitric acid or h3 bromite from 8-methyladipic acid and from the decomposition products of glyceric add and pyruvic add. The method described above is a modification of that of Higginbotham and Lapworth. ... 

A MIXTURE of 100 g. (0.88 mole) of citraconic anhydride (p. 28) (Note i), 100 cc. of water, and 150 cc. of dilute nitric acid (i part of concentrated nitric add to 4 parts of water by volume) is evaporated in a 500-cc. Erlenmeyer flask until the appearance of red fumes (Note 2). The solution is cooled and the mesaconic acid is collected on a filter. The mother liquor is evaporated to 150 cc., cooled, and the crystalline solid which separates is collected on a filter. Further concentration of the mother liquor to 50 cc. yields more product (Note 3). The entire product is recrystallized from 100 cc. of water. The yield of product melting at 203-205° is 50-60 g. (43-52 per cent of the theoretical amount). 

Mesaconic acid has been prepared by heating citraconic acid with dilute nitric add, with hydriodic acid, or with concentrated sodium hydroxide solution by heating a concentrated water solution of itaconic or dtraconic add at 180-200° by treating citradibromopyrotartaric add and mesodibromopyrotartaric acid with potassium iodide and copper at 150° and by heating dtraconic anhydride with nitric acid. ... 

On the other hand, double bonds activated by two carboxylic acid groups are seldom accepted also by ene reductases, though they are considered borderline substrates [25,121]. For instance, citraconic add was shown to afford (iJ)-2-meth-ylsucdnic add with a few OYEs, while mesaconic acid has been reduced only by EBPl yielding the (S)-enantiomer vdth less than 50% ee [28]. Anyway, the reaction is much less efficient compared to the corresponding diesters. 

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