Carboxylic acids commercial sources

Unless the last-mentioned product is removed by the inclusion of catalase, the oxoacid is liable to react further, undergoing oxidative decarboxylation to the carboxylic acid. An attractive feature of this group of enzymes in the present context is that there exist readily available representatives of both enantiospecificities. The well-studied and commercially available AAOs from vertebrate sources, such as l-AAO from snake venom and D-AAO from pig kidney, are expensive, however, and are increasingly being replaced by enzymes from microbial sources. 

Furan carboxylic acids are usually prepared by ring synthesis using the Feist-Benary and Paal-Knorr methods (Section 3.12.2.2). However, furancarboxylic acids can also be prepared by reaction of lithiofurans with carbon dioxide. A convenient source of furan-3-carboxylic acid (517) is the commercially available diethyl furan-3,4-dicarboxylate (518) (71S545). 

The obvious approach for chiral synthesis would be to find a chiral starting material, such as a natural amino acid, carbohydrates, carboxylic acids or terpene. The major source of these chiral starting materials sometimes called chirons is nature itself. The synthesis of a complex enantiopure chemical compound from a readily available enantiopure substance such as natural amino acids is known as chiral pool synthesis. For example, chiral lithium amides 1.39 that are used for several types of enantioselective asymmetric syntheses can be prepared in both enantiomeric forms starting from the corresponding optically active amino acids, and these are often available commercially. 

Materials. The following were obtained from commercial sources Swims medium S77, horse serum, and fetal calf serum (Grand Island Biologicals) MTX (Lederle Laboratories) was purified by DEAE cellulose prior to use (11) crystalline BSA, poly-L-lysine (M 35,000), hypoxanthine and thymidine (Sigma Chemical Co.) 1-etnyl-3-(3 -dimethylaminopropyl)carbodiimide hydrochloride (EDC) (Story Chemicals) folinic acid (ICN Pharmaceuticals) Blue Dextran (Pharmacia). The concentrations of the folate derivatives and MTX were determined by their respective extinction coefficients (13). MTX-BSA was synthesized according to a previously described procedure ( ) in which MTX is coupled via a terminal carboxyl group to -amino groups contained in the albumin molecule. 

Biosynthetically, purines are built up via formation of the imidazole ring first, from glycine and formate, and thence to hypoxanthine and then the other natural purines. In the laboratory, most imidazole-based purine syntheses start with 5-aminoimidazole-4-carboxylic acid, particularly its amide (known by the acronym AICA), which as well as its riboside, is commercially available from biological sources. The use of 5-aminoimidazole-4-carbonitrile in this approach results in the formation of 6-amino-purines, as in a synthesis of adenine itself." ... 

A large number of organic peroxides and hydroperoxides are known. Peroxo carboxylic acids, e.g., peracetic acid, CH3CO OOH, can be obtained by action of H202 on acid anhydrides. Peracetic acid is commercially made as 10-55% aqueous solutions containing some acetic acid by interaction of 50% H202 and acetic acid, with H2S04 as catalyst at 45-60° the dilute acid is distilled under reduced pressure it is also made by air oxidation of acetaldehyde. The peroxo acids are useful oxidants and sources of free radicals, c.g., by treatment with Fc2 l"(aq). Benzoyl peroxide and cumyl hydroperoxide are moderately stable and widely used as polymerization initiators and for other purposes where free-radical initiation is required. 

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