Malic acid, structure

Maleic acid, structure of, 753 Malic acid, structure of, 753 Walden inversion of, 359-360 Malonic ester, carboxylic acids from, 856-858... 

Fumaric acid is converted to L-malic acid by hydration in the presence of the enzyme fumamse. From the structure of the substrate and the configuration of the product, it is apparent that the hydroxyl group has been added to the si fiice of one of the carbon atoms of the double bond. Each of the trigonal carbon atoms of an alkene has its fiice specified separately. The molecule of fumaric acid shown below is viewed fixjm the re-re fiice. 

The name, maleic anhydride, came about in the same fashion. as any number of compounds early in the petrochemical Business Many organic acids and their derivatives were given common names based on some early observations, their special source in nature, or on some special feature of their structure. MA was first isolated in the 1850—75 era by dehydration of malic acid, a sugar acid found in apple juice. The Latin word for apple is malum. Hence, malum, malic, maleic. The suffix, anhydride, which follows each alias of MA, has a simple definition a compound derived by the loss of a molecule of water from two carboxyl groups (-COOH). 

The absolute configuration of the major isomers of spirolactone 102 and amide 103 was ISySRyl R, based on the known configuration of malic acid and determination of the relative configuration by an X-ray structure analysis of amide 103 [62]. 

The direction of enantio-differentiation (the predominant enantiomer R or S, to be produced) is decided by two factors. One factor is the configuration of the chiral structure, that is, if the catalyst modified with (S)-glutamic acid [(S)-Glu-MRNi] produces (R)-MHB from MAA, then (R)-Glu-MRNi produces (S)-MHB (2). The other factor is the nature of X. That is, when the amino acid or hydroxy acid with the same configuration is used as the modifying reagent, the configurations of the predominant products are enantiomers of each other in most cases. For example, (S)-aspartic acid-MRNi produces (R)-MHB and (S)-malic acid-MRNi produces (S)-MHB (19). 

Antohi (34) has reported several possible isozyme structures of a malic acid decarboxylating enzyme in Bacillus subtilis, and Peak (35) has reported the same in Euglena gracilis this must be kept in mind for the Leuconostoc oenos system. It is possible that the enzymatic activities that we have reported (6,7,8) may be the result of isozyme interactions of the same protein. 

HYDROXY DICARBOXYLIC ACIDS. Many natural and synthetic organic compounds arc hydroxy dicarboxylic acids. This article discusses mainly malic and tarrarie acids thiomalic acid is included because of its structural similarity to malic acid. 

There are very many enantiomerically pure starting materials available cheaply from nature. The amino acids are varied in structure and the hydroxy acids such as malic acid 11 and lactic acid 13 provide another resource. We shall give just one example of this kind of synthesis. Ethyl lactate 14 can be converted into the mesylate (a leaving group like tosylate) 15 and then reduced to the... 

Use of unmodified starches in combination with mild acids and carbonates has been claimed.214 Starch moisture content should be no greater than 25%. Acids such as tartaric, citric or malic acids are added at levels between 0.2% and 7%, while the carbonate level is 0.1% to 2%, both based on total starch composition. The acid is stated to serve a two-fold function it depolymerizes the starch during extrusion via hydrolysis, improving expansion at the same time, it liberates carbon dioxide, which acts as a blowing agent, from the carbonate. A typical formula extruded in a twin-screw extruder at 170-195°C yielded a product with a density of approximately 1 lb/ft3 (16kg/m3) and resilience of 60-85%. The foam had a continuous skin with a closed cell structure. 

Examples of alkylation of malic esters are listed in Table I, together with those of double alkylation, which can also be achieved, see 2 4 in Scheme 1. Since the (S) and the (R) forms of malic acid are both readily available,18 the enantiomers of all structures shown in Table I can be... 

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