A*Ketocarboxylic acid

In another procedure, D-amino acid oxidase (52) is usehil to produce L-amino acids from DL-amino acids. a-Ketocarboxylic acids which are formed by the action of enzymes on D-amino acids, are aminated to form L-amino acids by coupling through the action of amino acid aminotransferases (53). 

Isatin is the inner anhydride (lactam) of a y-amino-a-ketocarboxylic acid, isatinic acid (A), and is converted into a salt of this acid by the action of alkali. The keto-group in position 3 can condense with many other substances, and for this reason isatin is manufactured on a technical scale and converted into valuable indigoid vat dyes. The magnificent thioindigo scarlet, which is obtained from isatin and a sulphur analogue of indoxyl (the so-called hydroxythionaphthene), may be taken as example qq... 

Thermal degradation prior to ionization can cause decarbonylation or decarboxylation of the analyte. Decarbonylation, for example, is observed from a-ketocarboxylic acids and a-ketocarboxylic acid esters, whereas decarboxylation is typical behavior of P-oxocarboxylic acids such as malonic acid and its derivatives and di-, tri-, or polycarboxylic acids. 

Another example of Ugi/Pictet-Spengler two-step procedure was employed by El Kaim et al. to prepare polycyclic 1,4-diketopiperazines 228 [69]. The four-component Ugi reaction of homoveratryl isocyanide 229 and a-ketocarboxylic acids 230 allows the formation of Ugi products, which were treated with trifluor-oactic acid to afford tricychc 2,5-diketopiperazines 228 in a Pictet-Spengler-type cyclization (Scheme 42). 

Wandrey C, Leuchtenberger W, Kula MR (1981) Process for the continuous enzymatic change of water soluble a-ketocarboxylic acids into the corresponding amino acids. US 4304858... 

Lithium diisopropylamide (LDA)-assisted nucleophilic substitution adjacent to the lactam carbonyl in 273 produced a-ketocarboxylic acids 274 (Scheme 114 <1998BML1973>). 

Products of the interaction of A.C-diaminoazoles with a-ketocarboxylic acids were described by most investigators to be structures of type... 

Ketene, 104, 232 Ketimines, 414 -Ketoacetals, 221 0-Keto allenes, 230, 231 a-Ketocarboxylic acids, 184 1 -Keto-7,7-dimethylnorcarane, 181 a-Keto esters, 237, 245 Ketones, 229, 274 Ketones, resolution, 58, 59... 

In gas-phase reactions zeolites are superior to non-zeolitic molecular sieves, metal phosphates, and metal oxides. Over the mildly acidic [B]-MFI (Si/B = 24) the synthesis of phenylpyruvic acid methyl ester yields up to 94 % at 200 °C and WHSV = 3 h 95 % product yield could be achieved with the cesium-doped material (0.6 % w w) [8]. With these concepts a-ketocarboxylic acid esters can be prepared from readily available feedstocks whereas conventional methods require the use of costly and environmentally problematical Grignard reactions. 

Hydrazones from diazonium salts a-Ketocarboxylic acid ester phenylhydrazones from /5-ketocarboxylic acid esters s. 2, 462, 813... 

Scheme 36. Homologation of carboxylic acids to a-ketocarboxylic acids [37]...

The advantages of the new process for a-ketocarboxylic acid ester under gas phase conditions are high yields, high service time of the catalyst, and a one-step reaction using easily available starting materials. In contrast, the known processes are very complicated, costly and environmentally hazardous via Grignard reactions of oxalic acids. 

Whilst on oxidation of oxoisoatisine (III) the ethylenic linkage in the allyl position to the secondary hydroxyl group is attacked, such reaction is not possible with dihydrooxoisoatisine (IV) instead, the primary hydroxyl group suffers initial oxidation (though slowly) and a monocarboxylic acid (X) results which may be further oxidized to a ketocarboxylic acid (XI), the ketonic group of which is readily detected by its ultraviolet absorption. 

Based on Ochiai s procedure for a-acetoxylation of ketones, Ishihara and coworkers have developed the hypervalent iodine-catalyzed oxylactonization of ketocarboxylic acids to ketolactones [18], Optimized reaction conditions consist of the treatment of a ketocarboxylic acid with iodobenzene (10 mol%), p-toluenesulfonic acid monohydrate (20 mol%) and mCPBA as a stoichiometric oxidant in nitromethane solution Scheme 4.3 shows as a representative example the cyclization of ketocarboxylic acid 4 to ketolactone 5. 

The reaction of iminium chlorides with diazonium salts occurs via addition to the diazo group. For example, reaction of an iminium chloride CLXXVII with p-nitrophenyldiazonium fiuoroborate yields the aryl-hydrazone of an a-ketocarboxylic acid amide CLXXVIII... 

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