Malic acid naturally occurring

Malic acid (IV) occurs naturally, and is the cause of the sharp taste in over-ripe apples. 

The optical activity of malic acid changes with dilution (8). The naturally occurring, levorotatory acid shows a most peculiar behavior in this respect a 34% solution at 20°C is optically inactive. Dilution results in increasing levo rotation, whereas more concentrated solutions show dextro rotation. The effects of dilution are explained by the postulation that an additional form, the epoxide (3), occurs in solution and that the direction of rotation of the normal (open-chain) and epoxide forms is reversed (8). Synthetic (racemic) R,.9-ma1ic acid can be resolved into the two enantiomers by crystallisation of its cinchonine salts. 

Occurrence. S(—)-Mahc acid occurs widely in biological systems. It is the predominant acid in many fmits (Table 4). However, malic acid occurs in relatively low concentrations, thus making its isolation from natural sources expensive and impractical. 

Whenever possible, the chemical reactions involved in the fonnation of diastereomers and their- conversion to separate enantiomers are simple acid-base reactions. For example, naturally occurring (5)-(—)-malic acid is often used to resolve fflnines. One such amine that has been resolved in this way is 1-phenylethylarnine. Amines are bases, and malic acid is an acid. Proton transfer from (5)-(—)-malic acid to a racemic mixture of (/ )- and (5)-1-phenylethylarnine gives a mixture of diastereorneric salts. 

Maleonitrile, l,2-dicyanoethylene-l,2-dithio-metal complexes, 6, 147 Malic acid metal complexes geochemistry, 6, 867 naturally occurring, 2,962 Malonic add... 

Different organic acids, primarily lactic acid, have been successfully used for decontamination of whole livestock carcasses, and the application of different organic acids used for decontamination has also been tested in the fruit and vegetable industry. Organic acids other than lactic acid that are known to have bactericidal effects are acetic, benzoic, citric, malic, propanoic, sorbic, succinic and tartaric acids (Betts and Everis 2005). The antimicrobial action is due to a reduction in the pH in the bacterial environment, disruption of membrane transport, anion accumulation or a reduction in the internal pH in the cell (Busta et al., 2001). Many fruits contain naturally occurring organic acids. Nevertheless, some strains, for example E. coli 0157, are adapted to an acidic environment. Its survival, in combination with its low infective dose, makes it a health hazard for humans. 

Hiemstra and co-workers reported the first example of an iodine-promoted allenyl N-acyliminium ion cyclization for the total synthesis of (+)-gelsedine, the enantiomer of the naturally occurring (-)-gelsedine [72], Compound 341 was prepared from (S)-malic acid. When 341 was dissolved in formic acid with a large excess of Nal and heated at 85 °C for 18 h, 343 was found to be the major product isolated in 42% yield. The latter was then successfully converted to (+)-gelsedine in a multi-step manner. Other routes without the allene moiety failed to provide the desired stereoisomer. The successful one-step transformation of 341 to 343 was key to the success of this synthesis. 

Until now, only a limited number of ionic hquids have been prepared from renewable sources. Eor instance, some anions were synthesized from naturally occurring hydroxy acids (lactic [55] and malic [56] acids) or proteinogenic amino acids [57], whereas cations were obtained from amino alcohols (choline [58] and ephedrine [59, 60]), hydroxy acids (lactic and tartaric acid [61]), amino acids [57], and terpenes [62-64]. 

These acids are found ready-made in nature in great numbers. Some of them occur as free acids (citric acid, tannic acid, malic acid), others as esters (products of acids and alcohols, such as fats and oils and the flavors of many fruits and the odors of many flowers). Still other of these organic acids are produced by the action of bacteria (acetic acid from wine or cider, lactic acid when milk turns sour, butyric acid in rancid hutter). 

Cinchona alkaloids, naturally ubiquitous /3-hydroxy tertiary-amines, are characterized by a basic quinuclidine nitrogen surrounded by a highly asymmetric environment (12). Wynberg discovered that such alkaloids effect highly enantioselective hetero-[2 -I- 2] addition of ketene and chloral to produce /3-lactones, as shown in Scheme 4 (13). The reaction occurs catalytically in quantitative yield in toluene at — 50°C. Quinidine and quinine afford the antipodal products by leading, after hydrolysis, to (S)- and (/ )-malic acid, respectively. The presence of a /3-hydroxyl group in the catalyst amines is not crucial. The reaction appears to occur... 

Maleic anhydride CAS. 108-3I-6. til, maleic acid [CAS 110-16-7]. (2), and I umarie acid [CAS 110-17-81. i3) are multifunctional chemical intermediates that lind applications in nearly every Held id industrial chemistry. Each molecule contains two acid carbonyl groups and a double bond in the u. position. Maleic anhydride and maleic acid are important raw materials used in the manufacture of phthalic-type alkyd and polyester resins, surface coatings, lubricant additives, plasticizers. copolymers, and agricultural chemicals [see Alkyd Resins Polymers, and Lubricant). Both chemicals derive their common names from naturally occurring malic acid. 

Occurring widely in nature, malic acid is closely associated with apples. It is the second major acid, after citric, found in citrus fruits and it is present in most berry fruits. Malic acid is slightly stronger than citric in perceived acidity, imparting a fuller, smoother fruity flavour. 

Resolution of organic bases is carried out by reversing the process just described using naturally occurring optically active acids, (—)-malic acid, for example. Resolution of alcohols, which we shall find to be of special importance in synthesis, poses a special problem since alcohols are neither appreciably basic nor acidic, they cannot be resolved by direct formation of salts. Yet they can be resolved by a rather ingenious adaptation of the method we have just described one attaches to them an acidic handle, which permits the formation of salts, and then when it is no longer needed can be removed. 

One of the two resulting enantiomorphs gave, on oxidation with nitric acid, the enantiomorph of naturally occurring (—)-malic acid. 

XXX) by reduction to XXXII and subsequent acetobromolysis, and this product was converted into the ( —)-diol XXXI, identical with the alkamine of natural valeroidine (III). Inversely, partial methylation 39b) of that diol gave the methiodide (XXXIII) of (— )-6(8-methoxy-tropine so that no breaking of the C-6—0 bond occurred during demethy-lation hence, the methoxyl and hydroxyl groups are both The degradation by nitric acid of the (+ )-2,4-dioximino-3-tropanone (39 a,b) furnished 25% of [Pg.280]

Malic acid (Figure 2.11) is an alpha hydroxy organic acid, widely found in apples and other fruits and is, therefore, sometimes referred to as a fruit acid or, more specifically, an apple acid. It is also found in plants and animals, including humans. Malic acid is also known as hydroxybutaneoic acid or hydroxysuccinic acid. It is a chiral molecule, the naturally occurring... 

Similar to fumaric acid, L-malic acid is also a naturally occurring four-carbon dicarboxyhc acid and an intermediate in the TCA cycle. It has been used in many food products, primarily as an acidulant. L-Malic acid is compatible with all sugars with low hygroscopicity and good solubihty. In addition, it has therapeutic value for the treatment of hyperammoemia and liver dysfunction and as a component for amino acid infusion. L-Malic acid has been the subject of interest because of its increased application in the food industry as a citric acid replacement and its potential use as a raw material for the manufacture of biodegradable polymers. 

A few hydroxy acids are very cheap. (S)-(+)-Lactic acid 33 occurs in milk, (f )-(-)-malic acid in apples, and both enantiomers of the very important tartaric acid 35 and 36 are reasonably cheap. (+)-Tartaric acid 35 is usually called natural as it occurs in grapes, but (-) -tartaric acid 36 is natural too as it occurs in the West African tree Bankinia reticulata. The other enantiomers of malic and mandelic acids are commercially available and are not that much more expensive. 

Ryback, an associate of Cornforth, solved the problem by determining the absolute configuration of a degradation product of the naturally occurring (+)-abscisic acid as shown in the bottom of Figure 2.19.54 He first converted (-F)-abscisic acid to C. Ozonolysis of C yielded D after further oxidation and methylation. Then, D was synthesized from (S)-malic acid. The synthetic D showed the same optical rotation as that of D obtained from (+)-abscisic acid. Therefore, S-configuration was assigned to (+)-abscisic acid.54... 

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