5- 5-phenylhydantoin

Benzaldehyde cyanohydrin is reacted with urea to displace the hydroxyl group of the cyanohydrin. That intermediate is treated with HCI to convert the urea nitrogen to a nitrile. The resultant imine is hydrolyzed to the phenylhydantoin. Alkylation with ethyl iodide gives ethotoin, as described by A. Pinner in Chem. Ber. 21, 2325 (1888). 

Fig. 2-15. Reversed-phase retention of the first eluted and the seeond eluted enantiomers of 5-methyl-5-phenylhydantoin as a funetion of mobile phase eomposition. The eolumn was a 250 x 4.6 mm vaneomyein CSR The buffer was triethylammonium aeetate at pH 7.0. The flow rate was 1.0 mL min at ambient temperature (23 °C).

Hydroxyphenylpyruvic acid has been prepared by alkaline hydrolysis of the azlactone of a-benzoylamino- -acetoxycin-namic acid 7 and by a two-step hydrolysis of the azlactone of a-acetamino- -acetoxycinnamic acid.8 p-Hydroxyphenylpyruvic acid has also been prepared by alkaline hydrolysis of 5-( -hy-droxybenzal)-3-phenylhydantoin.9 The procedure described here is adapted from published directions for the preparation of -hydroxyphenylpyruvic-3-C14 acid.5 5-( -Hydroxybenzal)hy-dantoin is prepared according to the method of Boyd and Robson.10... 

Hydroxyphenylpyruvic acid plays an important role in the biogenesis of compounds with a phenylpropane skeleton, and it has been used as substrate in several enzyme studies. Published procedures for its preparation are unsatisfactory in many ways. The alkaline hydrolysis of the azlactone of a-bcnzoylamino- -acetoxycinnamic acid 7 makes necessary a tedious separation of the resulting benzoic acid, and the yield is only 34% based on -hydroxybenzaldehyde. The hydrolysis of 5- ( -hydroxybenzal)-3-phenylhydantoin 9 requires a separation of phenylurea. Finally, the two-step cleavage of the azlactone of a-acetamino- -acetoxycinnamic acid 8 does not proceed easily, and impure products are obtained. In applying this procedure to the synthesis of a carboxyl-labeled -hydroxyphenylpyruvic acid, the overall yield was only 9%.u It must be kept in mind that any prolonged isolation procedure will cause some decomposition of this sensitive compound. 

Phenylpyruvic acids by hydrolysis of phenylhydantoins, 43, 49 1-Phenyl-2-THiOBiuRET, 42, 87 l-Phenyl-2-thio-4-ethylisobiuret, 42, 89 l-Phenyl-2-thio-4-methylisobiuret, 42, 87... 

Amino acid sequencing may be carried out in a number of ways. The most widely used is the Edman degradation procedure in which phenylisothiocyanate is used to react with the amino acid residue at the amine end of the protein chain. This derivatized residue is removed from the remainder of the protein and converted to a phenylhydantoin derivative which is identified by using, for example, HPLC. 

Other ring closure reactions that have been studied include those of 5-phenylhydantoic acids to 3-phenylhydantoins in aq. H2S04 solutions at 70°C.249 The low m values observed suggest a mechanism that involves C-N... 

V-Subslilulion and 5,5-disubstitution prevent ring opening as demonstrated by various examples. Ethotoin (3-ethyl-5-phenylhydantoin, 4.230), in contrast to its /V-dcclhylalcd metabolite, was not detectably hydrolyzed by DHPase. No ring-opened metabolite was found for phenytoin (5,5-diphenyl-hydantoin, 4.231) or nirvanol (5-ethyl-5-phenylhydantoin, 4.232), which is the AT-demethylated metabolite of mephenytoin (4.233) [144],... 

Infants whose mothers have been treated with certain anticonvulsants during pregnancy (phenylhydantoins)... 

The principal metabolite of phenytoin is 5-(p-hydroxyphenyl)-5-phenylhydantoin (parahydroxy phenytoin) which, as the glucuronate, forms over 70% (65-81%) of the urinary excretion products. Free phenytoin accounts for less than 5% of the total (G9). Little phenytoin is excreted in the feces although free and hydroxylated phenytoin are excreted into the saliva and bile (N5). 

Ethotoin Ethotoin, 3-ethyl-5-phenylimidazolidine-2,4-dione (9.1.5), is synthesized in basically the same manner as described above, which in this case involves the reaction of benzaldehyde oxynitrile (9.1.2), with urea or ammonium hydrocarbonate, which forms the intermediate urea derivative (9.1.3) which on acidic conditions (9.1.3) cycUzes to 5-phenylhydantoin (9.1.4). Alkylation of this product using ethyliodide leads to the formation of ethotoin (9.1.5) [3,4]. 

Valine.—This amino acid is contained mixed with leucine in the fractions of the esters which boil between 6o° and 90° C. Its isolation and separation from leucine is of extreme difficulty, since these compounds, as well as their copper salts into which they are converted by boiling with freshly precipitated cupric oxide, tend to form mixed crystals. Its isolation was only effected by these means in certain cases, and its amount is really much more than the figures represent from its yield. It is best characterised by conversion into its phenylhy-dantoine derivative by treatment with phenyl isocyanate in alkaline solution. The phenylureido acid is first formed, and this loses a molecule of water, as shown by Mouneyrat, and is changed into its anhydride or phenylhydantoine by treatment with hydrochloric acid. The following reactions occur —... 

As thus obtained, the proline is a mixture of the optically active and the racemic forms these are separated by conversion into their copper salts and treatment with absolute alcohol which dissolves that of the optically active proline. Their purification is easy, and a determination of the water of crystallisation and of the copper establishes the identity of the compound. The phenylhydantoine derivative may also be used for this purpose. 

Assumptions Synthesis of phenylpyruvic acid Batch synthesis process for precursors overal yield of 95+% of theoretical to pheny Ihydantoin overall yield of 90+% of theoretical from phenylhydantoin to phenylpyruvic acid recovery and recycle of acetic acid no byproduct crec taken for acetic acid formed from acetic anhydride addition. Conversion of phenylpyruvic acid and aspartic acid. Bioreactor productivity of-18 g PHE/L/h (four columns in parallel) 98% overall conversion no byproduct credit taken for pymvic acid (recovery cost assumed to be of by revenue from sale) 80% recovery of L-PHE downstream of bioreactor. 

Oddly, one area in which GLC is used for separation of amino acid derivatives, appears to have great potential for applications of liquid chromatography. The phenylhydantoins produced in sequence determination have ultraviolet absorbance and are efficiently separable by high-performance liquid chromatography (64). Their GLC separations are less than optimum and it is likely that new developments in this area will include liquid chromatographic separations. 

The internal standard for sedative analysis is 10 pi of methyl laurate in 1 cm3 pyridine. The internal standard for Dilantin analyses is 1 mg of 5-(p-methyl, phenyl)-5-phenylhydantoin in 100 cm3 chloroform. 

The separation of several amino acid phenylhydantoins by HPLC. Courtesy of Rainin Instrument Co., Woburn, MA. 

TABLE 5 Effects of the Substituents on the Chiral Resolution of 5-Alkyl-5-phenylhydantoin Enantiomers on a / -CD Phase... 

FIGURE 7 Effect of mobile phase composition on the resolution of enantiomers of different racemates in reversed-phase HPLC on antibiotic CSPs. (a) First ( , O) and second ( , ) enantiomers of 5-methyl-5-phenylhydantoin on a Chirobiotic T column using an acetonitrile-triethylammonium acetate buffer (—) and a methanol-triethylammo-... 

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