Citraconic acid anhydride

The rate of hydrolysis is affected by the amino acid that follows the basic residue in the sequence. Thus the Arg-Asp bond is cleaved more slowly than most other peptide bonds on the right side of arginine. Similarly, the bond between arginine and cysteic acid (the oxidized form of cysteine) is relatively resistant to tryptic hydrolysis. As it will be shown later such differences can be exploited in sequence studies, but it is possible to create even more substantial differences by appropriate modifications of the peptide molecule. For instance, treatment of a peptide that contains both lysine and arginine residues with maleic acid anhydride or preferably with citraconic acid anhydride yields derivatives in which the lysine residues have no free amino group in their side chain... 

Condensation with Aldehydes and Ketones. Succinic anhydride and succinic esters in the presence of different catalysts react in the gas phase with formaldehyde to give citraconic acid or anhydride and itaconic acid (94—96). Dialkyl acyl succinates are obtained by reaction of dialkyl succinates with C 4 aldehydes over peroxide catalysts (97). 

As for the reaction path from pyruvic acid to citraconic anhydride, it is considered that a condensation reaction first takes place by a reaction between an oxygen atom of carbonyl group and two hydrogn atoms of methyl group in another molecule, followed by oxidative decarboxylation to form citraconic acid. The produced citraconic acid is dehydrated under the reaction conditions used. The proposed reaction path is shown in Figure 7. 

Part 24 Determination of maleic acid and maleic anhydride in food simulants Ion pair HPLC of maleic acid with cetyl trimethyl ammonium chloride and UV detection (245 nm) with citraconic acid as internal standard... 

Citraconic anhydride (or 2-methylmaleic anhydride) is a derivative of maleic anhydride that is even more reversible after acylation than maleylated compounds. At alkaline pH values (pH 7-8) the reagent effectively reacts with amine groups to form amide linkages and a terminal carboxylate. However, at acid pH (3-4), these bonds rapidly hydrolyze to release citraconic acid and free the amine (Figure 1.86) (Dixon and Perham, 1968 Habeeb and Atassi, 1970 Klapper and Klotz, 1972 Shetty and Kinsella, 1980). Thus, citraconic anhydride has been used to temporarily block amine groups while other parts of a molecule are undergoing derivatization. Once the modification is complete, the amines then can be unblocked to create the original structure. 

On similar reasonings the configuration of citraconic acid is cis because it forms the anhydride while its isomer mesaconic acid is trans. 

B. Citraconic Acid To 22.4 g. (0.2 mole) of pure citraconic anhydride in a 100-cc. beaker is added from a pipette exactly... 

The crude citraconic anhydride contains a small amount of water, acetone and citraconic acid. Vacuum distillation allows the removal of these impurities without materially decreasing the yield. 

Citraconic anhydride has been prepared by the distillation of citraconic acid and of citric acid.1... 

Itaconic acid has been prepared by the distillation of citric acid,2 of aconitic acid,3 and of itamalic add 4 by heating dtric acid with dilute sulfuric acid in a closed tube 5 by treating aconitic acid with water at 1800 6 by heating citraconic acid with sodium hydroxide 7 by heating citraconic anhydride with water at 1500 8 and by heating a concentrated solution of citraconic add at 120-130° in a sealed tube.9... 

Mesaconic acid has been prepared by heating citraconic acid with dilute nitric acid, with hydriodic acid,2 or with concentrated sodium hydroxide solution 3 by heating a concentrated water solution of itaconic or citraconic acid at 180-200° 4 by treating citradibromopyrotartaric acid and mesodibromopyrotartaric acid with potassium iodide and copper at 1500 5 and by heating citraconic anhydride with nitric acid.6... 

Figure 2. Effect of cyclic acid anhydride concentration on the modification of e-NH2 groups in the yeast proteins maleic anhydride (O) citraconic anhydride (%).

The product from the reaction of citraconic acid (or its anhydride) with nitric acid was initially assigned the structure of 3-methyl-5-(l,l,2-trinitroethyl)isoxazole [588], However, it was subsequently established that this compound was 5-methyl-4-nitro-3-(l,l-dinitroethyl)isoxazole [589], As mentioned earlier, the antibiotic azomycin (2-nitroimidazole) and some of its derivatives can be obtained by microbiological synthesis [331, 450, 590, 591],... 

Citraconic anhydride is hydrolyzed to the cis unsaturated dibasic acid, citraconic acid, by heating with the theoretical amount of water until the mixture is homogeneous. Hydrolysis by dilute nitric acid gives the trans acid, mesaconic acid. ... 

Nitrobenzenethiol will add across the double bond of maleic anhydride124 the adduct can then be cyclized in the presence of zinc and acetic acid to give l,4-benzothiazin-3-one-2-acetic acid (82). Similar studies with citraconic acid and the acid anhydride, where the thiol added predominantly to the position ft to the methyl in contrast to an earlier report,125 gave the citraconic anhydride and acid adducts. When treated with zinc and acetic acid, the adducts formed diastereoisomers (83a and 83b) of 1,4-benzothiazin-3-onepropanoic acid. 

Citraconic Acid. 2-Methyi-2-butenedioic acid methylmaleic acid. C H604 mol wt 130.10. C 46.16%, H 4-65%, O 49.19%. Obtained by carefully heating citric acid at about 175. Production o( citraconic anhydride from ita -conic acid Humphrey. U.S. pat. 2.966,498 (i960 to Pfizer). 

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