Of glyoxylic acid

A weak cation-exchange resin is obtained by reaction of glyoxylic acid and a cross-linked polyvinyl alcohol. The polyvinyl alcohol is cross-linked with glutaraldehyde in the presence of hydrochloric acid. The cation-exchange resin has an exchange capacity of 3 meq/g or greater and a swelling volume of 10 ml/g or smaller (37-38). 

With semicarbazones of lower a-keto acids the reaction proceeds with some difficulty or not at all. Thus, the semicarbazones of pyruvic acid cannot be cyclized and that of glyoxylic acid is predominantly hydrolyzed so that the yield of the cyclization product is only 20-25%. ° This reaction was used in work with a different object, for preparing 6-azauracil, for the first time. 

In a further synthesis, Gut ° used the cyclization of the thiosemi-carbazone of glyoxylic acid (56) the 2-thioxo-5-oxo-2,3,4,6-tetra-hydro-l,2,4-triazine (57) formed was converted to 6-azauracil by applying aqueous solution of chloroacetic acid. (This reaction will be discussed later, e.g.. Section II,B,4,b.) The same procedure was used... 

A uniformly favorable effect is displayed by an alkyl group, in position 2. Thus the 2-methylthiosemicarbazone of pyruvic acid is cyclized at normal temperature and without excess hydroxide. The 2-methylthiosemicarbazone of glyoxylic acid (98) was cyclized by boiling for 5 min to 2-methyl-3-thioxo-5-oxo-2,3,4,5-tetrahydro-... 

Mesoxalic dialdehyde can be reasonably expected (16,28,50) to undergo normal glycol cleavage and give one mole of formic acid and one mole of glyoxylic acid in fact, when a second molar equivalent of periodate was added to the above solution, two molar equivalents of titratable acid were formed. If an excess of periodate is now added, two molar equivalents of titratable acid remain, but in addition, one molar equivalent of carbon dioxide can be expelled from the solution. Thus, in the overall reaction, one mole of triose reductone is oxidized by three moles of periodate to give two moles of formic acid and one mole of carbon dioxide ... 

The fact that only Grignard reagents add with high diastereoselectivity to the phenylmenthyl ester of glyoxylic acid, whereas methyllithium reacts nonstereoselectively, may be the result of a different aggregation of the reagents. This is supported by the tremendous improvement of the stereoselectivity when the addition of methyllithium is undertaken in the presence of lithium perchlorate13. 

Bronsted-acid-catalyzed Diels-Alder reactions are not frequent because of the proton sensitivity of many dienes and cycloadducts, especially when long reaction times and high temperatures are required. Examples in aqueous medium involving imines activated by protonation as dienophiles and a proton-promoted Diels-Alder reaction of glyoxylic acid with cyclopentadiene are considered in Section 6.1. 

C-Disaccharide analogs of trehalose were recently [20c] prepared by using as a key step an aqueous Diels-Alder reaction between the sodium salt of glyoxylic acid and the water soluble homochiral glucopyranosil-l,3-pentadiene 19 (Equation 6.1). A mixture of four diastereoisomers in a 41 24 21 14 proportion was obtained after esterification with methanol and acetylation. The main diaster-eoisomer 20 was isolated and characterized as benzoyl-derivative. 

The cycloaddition of glyoxylic acid with cyclopentadiene in water at pH 6 and 60 °C is slow and occurs with low yield and low diastereoselectivity [18] (Scheme 6.17). Proton (pH = 0.9) [18], copper salts [27] and Bi(OTf)3 [28] accelerate the reaction and increase the diastereoselectivity. The lactones 28 and 29 originate from endo and exo cycloadducts 27, respectively. The proposed rearrangement is depicted in Scheme 6.17 for the major endo adduct 30. A competitive ene reaction that originates 28 and 29 cannot be excluded [28]. 

DuPont has developed a process for the manufacture of glyoxylic acid by aerobic oxidation of glycolic acid (Fig. 2.33) mediated by whole cells of a recombinant methylotrophic yeast (Gavagnan et al, 1995). The glycolic acid raw material is readily available from the acid-catalysed carbonylation of formaldehyde. Traditionally, glyoxylic acid was produced by nitric acid oxidation of acetaldehyde or glyoxal, processes with high E factors, and more recently by ozonolysis of maleic anhydride. 

Addition to oxime ethers of glyoxylic acid generates A-benzyloxyamino acids. These reactions have been done in both organic solvents344 and aqueous mixtures.345 The reactions can be done with or without Bu3SnH as a chain carrier. 

This mechanism is supported by the fact that a secondary hydrazone such as (8) yields the azohydrazone (9) rather than the formazan.8 Ketone hydrazones also yield azohydrazones. The coupling of hydrazones of glyoxylic acid (10) with diazonium salts is accompanied by decarboxylation to yield 3-unsubstituted formazans (11). Similarly, hydrazones of mesoxalic acid (12) yield formazans with a carboxyl group in position 3, e.g., 13 (Scheme 2).910 Both 11 and 13 can react with diazonium salts to yield the... 

A study of, and details of how to control, the stop-start nature of the oxidation of formic acid. Probably relevant to other nitric acid oxidations, especially preparation of glyoxylic acid from glyoxal. 

Both the anodic and cathodic reactions lead to the same final product, (Fig. 2D), e.g. simultaneous anodic and cathodic production of glyoxylic acid [57]. 

Preparation of 2-unsubstituted products by this method would require the use of formaldehyde as the aldehyde component, which gives low yields. However, the use of glyoxylic acid, either as the free acid or bound to macroporous polystyrene carbonate, results in satisfactory formation of the 2-unsubstituted products through an in situ decarboxylation <2004OL4989>. The use of a nonpolar solvent (toluene) has been reported to reduce the formation of side products in this type of reaction <2006TL947>. 

Fig. 4.15. Synthesis of KDO using ethyl diazoacetate as synthetic equivalent of the anion of glyoxylic acid ethyl ester [980].

C. Crotyl diazoacetate. A solution of 10.0 g. (0.038 mole) of the />-toluenesulfonylhydrazone of glyoxylic acid chloride in 100 ml. of methylene chloride is cooled in an ice bath. Crotyl alcohol (2.80 g. or 0.038 mole) (Note 7) is added to this cold solution, and then a solution of 7.80 g. (0.077 mole) of redistilled triethyl-amine (b.p. 88.5-90.5°) in 25 ml. of methylene chloride is added to the cold reaction mixture dropwise and with stirring over a 20-minute period. During the addition a yellow color develops in the reaction mixture and some solid separates near the end of the addition period. The resulting mixture is stirred at 0° for 1 hour and then the solvent is removed at 25° under reduced pressure with a rotary evaporator. A solution of the residual dark orange liquid in approximately 200 ml. of benzene is thoroughly mixed with 100 g. of Florisil (Note 8) and then filtered. The residual Florisil, which has adsorbed the bulk of the dark colored by-products, is washed with two or three additional portions of benzene of such size that the total volume of the combined benzene filtrates is 400-500 ml. This yellow benzene solution of the diazoester is concentrated under reduced pressure at 25° with a rotary evaporator, and the residual yellow liquid is distilled under reduced pressure. (Caution This distillation should be conducted in a hood behind a safety shield) (Note 9). The diazo ester is collected as 2.20-2.94 g. (42-55%) of yellow liquid, b.p. 30-33° (0.15 mm.), n T) 1.4853 - 1.4856 (Note 10). 

Although the present procedure illustrates the formation of the diazoacetic ester without isolation of the intermediate ester of glyoxylic acid />-toluenesulfonylhydrazone, the two geometric isomers of this hydrazone can be isolated if only one molar equivalent of triethylamine is used in the reaction of the acid chloride with the alcohol. The extremely mild conditions required for the further conversion of these hydrazones to the diazo esters should be noted. Other methods for decomposing arylsulfonyl-hydrazones to form diazocarbonyl compounds have included aqueous sodium hydroxide, sodium hydride in dimethoxyethane at 60°, and aluminum oxide in methylene chloride or ethyl acetate." Although the latter method competes in mildness and convenience with the procedure described here, it was found not to be applicable to the preparation of aliphatic diazoesters such as ethyl 2-diazopropionate. Hence the conditions used in the present procedure may offer a useful complement to the last-mentioned method when the appropriate arylsulfonylhydrazone is available. 

Shortly before Hopkins and Cole isolated tryptophane, they studied the Adamkiewicz reaction—the production of a violet colour when concentrated sulphuric acid is added to a protein dissolved in glacial acetic acid—and found that it was caused by the presence of glyoxylic acid in the glacial acetic acid, from which it arose by the action of sunlight. On applying the glyoxylic reaction to tryptophane a very intense colour was produced, and hence the presence of tryptophane in the protein molecule is the cause of this reaction. 

Homogenization with NaOAc solution at 100°C for lOmin Enzymatic digestion with acid phosphatase, papain, amylase, glucosidase with addition of glyoxylic acid, ferrous sulfate solution and Gh at 37°C for 18h centrifugation ... 

In the reactions of 4-amino-l-azadienes 295 with esters of glyoxylic acid, chemoselective cyclization occurred with displacement of the amino group NHR, and 2/7-1,3-oxazine-2-carboxylic acid derivatives 296 were formed in high yields instead of the corresponding 1,2-dihydropyrimidines usually obtained in the reactions of 295 with aliphatic or aromatic aldehydes (Equation 28) <1996T3095>. 

Olson, T. M., and M. R. Hoffmann, Formation Kinetics, Mechanism, and Thermodynamics of Glyoxylic Acid-S(IV) Adducts, . /. Phys. Chem., 92, 4246-4253 (1988a). 

The statine-like moiety in one of the first drugs, saquinovir (23-8), comprises a transition state mimic for the cleavage of phenylalanylprolyl and tyrosylprolyl sequences. Constmction starts with the protection of the amino group of phenylalanine as its phthaloyl derivative (Phth) by reaction with phthalic anhydride this is then converted to acid chloride. The chain is then extended by one carbon using a Friedel-Crafts-like reaction. The required reagent (21-2) is prepared by reaction of the enolate obtained from the /7A-silyl ether (21-3) of glyoxylic acid and lithio... 

Cycloaddition of esters of glyoxylic acid occurs only with the trams-... 

Figure 10.4. Preparation of glyoxylic acid derived imines [130].

Results are shown in figure 4. The conversion reaches 66% after seven hours of electrolysis. The main product is FA (99%) and no selectivity i<. observed towards the formation of glyoxylic acid. Otherwise, conversely to the previous electrolysis in perchloric acid medium (pH=l), no trace of CO2, neither in the gas phase nor in solution as C03=, is observed. Therefore, the oxidation of glyoxal stops at the FA stage. This was confirmed by a voltammetric study, which showed that FA is not electroreactive above 1.0 V/RHE. The FA produced during the electrolysis at 1.9 V/RHE does not undergo further oxidation. 

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