Reaction with malic acid

As in the case of lactic acid, incorporation of the 1-carboxyl and 2-hydroxyl groups into a dioxolanone ring increases the susceptibility of the hydroxyl-bearing carbon to substitution reactions. With malic acid, dioxolanone 170 can be readily alkylated in a highly stereoselective fashion to furnish alkylated dioxolanones 206 with diastereoselectivity surpassing 95% (Scheme 27) [59]. 

Make acid yields coumaUc acid when treated with fuming sulfuric acid (19). Similar treatment of malic acid in the presence of phenol and substituted phenols is a facile method of synthesi2ing coumarins that are substituted in the aromatic nucleus (20,21) (see Coumarin). Similar reactions take place with thiophenol and substituted thiophenols, yielding, among other compounds, a red dye (22) (see Dyes and dye intermediates). Oxidation of an aqueous solution of malic acid with hydrogen peroxide (qv) cataly2ed by ferrous ions yields oxalacetic acid (23). If this oxidation is performed in the presence of chromium, ferric, or titanium ions, or mixtures of these, the product is tartaric acid (24). Chlorals react with malic acid in the presence of sulfuric acid or other acidic catalysts to produce 4-ketodioxolones (25,26). 

Coumarin can also be formed by the reaction of phenol with diketene (40). Similarly, diphenols can react with hydroxycarboxyUc acids or beta-ketoesters to give hydroxycoumaria derivatives. The reaction of resorciaol with malic acid produces umbeUiferone (7-hydroxycoumaria) and its reaction with ethyl acetoacetate gives beta-methylumbeUiferone (7-hydroxy-4-methylcoumaria). 

In 1896, the German chemist Paul Walden made a remarkable discovery. He found that the pure enantiomeric (+)- and (-)-malic acids could be intercon-veited through a series of simple substitution reactions. When Walden treated (-)-malic acid with PCl5, he isolated (4-)-chlorosuccinic acid. This, on treatment with wet Ag20, gave (+)-malic acid. Similarly, reaction of (+)-malic acid with... 

The student may wonder just what the mechanism is in cases where retention of configuration is involved since it certainly is not simple Sn2. As we shall see later, the reaction between malic acid and thionyl chloride is an SNi process (p. 420), while a neighhoring-group mechanism (p. 404) is involved in the treatment of chlorosuccinic acid with silver oxide. 

Tikhonova et al. (1981) studied the combined catalytic action of Ce(III, IV) and Mn(II, III) in oscillating redox reaction in the B-Z system by measuring Br potential. As catalysts, both metal ions act independently. Similar to Tikhonova et al. (1981), Ramaswamy et al. (1980) examined the system of combined Mn(III)/Mn(II) and Ce(IV)/Ce(III) with malic acid as substrate, and followed the oscillating potentials of a platinum electrode. 

Heating the mixture of isomers of 109 with TsOH equilibrates the diastereoisomers so that the required more stable syn (H and Et syn) diastereoisomer of 109 crystallises out. Treating this with (+) malic acid leads to crystals of the natural enantiomer (+)-sy -109. Both the unwanted anti-diastereoisomer and the unwanted enantiomer can be equilibrated again with TsOH. This cannot be enolisation as there are no a-hydrogens and is presumably equilibration by reversible Mannich reaction as 110 lacks either stereogenic centre and so epimerises both ... 

A stopped-flow method has been used to study the reactions of the [Fe(H20) ] ion with the a-hydroxy-carboxylic acids glycolic, DL-lactic, DL-malic, and benzilic acids. The main pathway involves reactions of [Fe(H20)5(0H)] + ion with HL, and an 7d mechanism is proposed. A similar study involves reactions with acetohydroxamic acid, hydroxyproline hydroxamic acid, tryptophane hydroxamic acid, and histidine hydroxamic acid. The second-order rate constants at 25 °C fall in the range (1.14—5.90) x 10 s. ... 

As is the case in decarboxylation reactions involving malic acid, histidine, and tyrosine, degrading arginine provides yeasts with additional energy resonrces. The net energy gain via the arginine pathway consists of a molecnle of ATP produced from carbamyl-P. 

A. G. Osborne obtained the structures of the angular 14 and linear 15 isomers from the Pechmann reaction of 7-hydroxy coumarin 9 with malic acid in the presence of sulfuric acid (Scheme 6) (83T1523). 

Malic Acid. When heated with cone, sulfuric acid and a small amount or resorcinol or orcinol, malic acid gives derivatives of umbelli-ferone, which fluoresce strongly in alkaline media. A very strong fluorescence is also observed on the reaction of malic acid with 2-naphthol (120). 

Optically inactive starting materials can give optically active products only if they are treated with an optically active reagent or if the reaction is catalyzed by an optically active substance The best examples are found m biochemical processes Most bio chemical reactions are catalyzed by enzymes Enzymes are chiral and enantiomerically homogeneous they provide an asymmetric environment m which chemical reaction can take place Ordinarily enzyme catalyzed reactions occur with such a high level of stereo selectivity that one enantiomer of a substance is formed exclusively even when the sub strate is achiral The enzyme fumarase for example catalyzes hydration of the double bond of fumaric acid to malic acid m apples and other fruits Only the S enantiomer of malic acid is formed m this reaction... 

As a dibasic acid, malic acid forms the usual salts, esters, amides, and acyl chlorides. Monoesters can be prepared easily by refluxing malic acid, an alcohol, and boron trifluoride as a catalyst (9). With polyhydric alcohols and polycarboxyUc aromatic acids, malic acid yields alkyd polyester resins (10) (see Alcohols, polyhydric Alkyd resins). Complete esterification results from the reaction of the diester of maUc acid with an acid chloride, eg, acetyl or stearoyl chloride (11). 

Alkyl hahdes in the presence of silver oxide react with alkyl malates to yield alkoxy derivatives of succinic acid, eg, 2-ethoxysuccinic acid, H00CCH2CH(0C2H )C00H (12,13). A synthetic approach to produce ethers of malic acid is the reaction of malic esters and sodium alkoxides which affords 2-alkoxysuccinic esters (14). 

Hand in hand with this research on finding a suitable carboxyUc acid chemical for cross-linker has been the search for an economical catalyst system. The catalyst found to be most effective for the esterification reaction was sodium hypophosphite (NaH2P02). This material was also costiy and out of range for the textile industry. Because weak bases function as catalyst, a range of bases has been explored, including the sodium salts of acids such as malic acid. 

From Phenol. In the type of condensation discovered by von Pechmaim in 1883, coumarin is formed by reaction of phenol [108-95-2] with malic (34), maleic, or fumaric acids (35—38) in the presence of concentrated sulfuric acid. 

At this point, it is desirable for us to see just how it was originally proved that a given substitution reaction proceeds with inversion of configuration, even before the mechanism was known. Walden presented a number of examples in which inversion must have taken place. For example, (+)-malic acid could be converted to ( + )-chlorosuccinic acid by thionyl chloride and to (— )-chlorosuccinic acid by phosphorus pentachloride ... 

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