Hydantoic acid

Hydrolysis. Although hydantoins can be hydroly2ed under strongly acidic conditions, the most common method consists of heating ia an alkaline medium to give iatermediate ureido acids (the so-called hydantoic acids), which are finally hydroly2ed to a-amino acids. 

Synthesis from OC-Amino Acids and Related Compounds. Addition of cyanates, isocyanates, and uiea derivatives to a-amino acids yields hydantoin piecuisois. This method is called the Read synthesis (2), and can be considered as the reverse of hydantoin hydrolysis. Thus the reaction of a-amino acids with alkaline cyanates affords hydantoic acids, which cyclize to hydantoins in an acidic medium. 

The yields of AEG were between 11 and 79%, at starting concentrations of 10 —10 4 M. AEG cyclizes to the lactam, monoketopiperazine, at neutral pH and around 373 K. The synthesis of the monomeric PNA units was carried out three years later (Nelson et al., 2000a, b). The synthesis of pyrimidine-A -acetic acid can be achieved if the reaction of cyanoacetaldehyde with high concentrations of urea mentioned above is modified slightly, with hydantoic acid replacing urea (Robertson and Miller, 1995). 

Hydantoin, the cyclic form of hydantoic acid, was detected in the Murchison meteorite and also as a product of polymerisation of HCN (Ferris et al 1974). The yields obtained (based on cyanoacetaldehyde) were 18% for cytosine-N -acetic acid, but only 1.8% for the corresponding uracil derivative (1 mM cyanoacetaldehyde and 2 M hydantoic acid were allowed to react at around 373 K). 

Fig. 6.13 Reaction routes for the synthesis of other components of PNA, such as cytosine- and uracilacetic acid (see Fig. 6.12) from hydantoic acid and cyanoacetaldehyde (Nelson et al., 2000b)...

Phenylurea. 1 Hydantoic acid. Ethyl hydantoate. Ethanol. " Reprinted in part from F. B. Slezak, H. Bluestone, T. A. Magee, and J. H. Wotiz, J. Org. diem ll, 2181 (1962). Copyright 1962 by the American Chemical Society. Reprinted by permission of the copyright owners. 

The conversion of urea to hydrazine using hypochlorite is known as Shestakov rearrangement.1731 It has been used to obtain a-hydrazino acids from a-amino acid derived hydantoic acids, with chiral retention but in a moderate yield (about 20-40%), using NaOCI.174,751 The use of KOC1, instead of NaOCl, greatly increases the yield of Shestakov rearrangement (Scheme 19).176-781... 

URECH HYDANTOIN SYNTHESIS. Formation of hydantoins from o -amino acids by treatment with potassium cyanate in a aqueous solution and heating of the salt of the intermediate hydantoic acid with 25% hydrochloric acid. 

E. C. Juenge, M. A. Kreienbaum, and D. F. Gurka, Assay nitrofurantoin oral suspensions contaminated with 3-(5-nitrofu ideneamino) hydantoic acid, J. Pharm. Sci., 74 100(1985). 

C40HMNKOK 40488-86-6) see Angiotensinamide hydantoic acid nitrile (C,H3N,0 5962-07-2) see Orotic acid hydantoin... 

Stella, V. Higuchi, T. Esters of hydantoic acids as prodrugs of hydantoins. J. Pharm. Sci. 1973, 62, 962-967. 

A large number of hydantoins and 2-thiohydantoins wtih substituents in the C-5 position as well as a limited number of N-l substituted examples have been prepared by this route. The ring closure of the hydantoic acid intermediates (1) to hydantoins (2) is reversible, the forward reaction being... 

Urea, methylurea, and dimethylureas react with glyoxylic acid and its methyl ester to give a-substituted hydantoic acid derivatives (16) and substituted allantoic acid derivatives (17), which can be cyclized to 5-substituted hydantoins (18). Although allantoin (18) formation from urea and... 

Juenge, E.C. Kreienbaum, M.A. Gurka, D.F. Assay of nitrofurantoin oral suspensions contaminated with 3-(5-nitrofurfurylideneamino)hydantoic acid. J.Pharm.Sci., 1985, 74, 100-102... 

The Strecker synthesis starting from a-amino nitriles and potassium cyanate yields useful hydantoins as intermediates. They are hydrolyzed at neutral pH to hydantoic acids and to amino acids (not shown) (Scheme 9.4.3)... 

The polymerization rate depends upon the concentration of the amine and the monomer. The degree of polymerization is often, but not always, equal to the ratio of the monomer to the amine. ft means that the reaction may be similar to, but not identical to, a living-type polymerization. In addition, the molecular weight distribution curve may be broadened or bimodal. This may be due to some chemical termination reactions. These can be intramolecular reactions of the terminal amine group with some functional group in the side chain and lead to formation of hydantoic acid end groups. It may also be due to physical termination from precipitation of the product. 

Figure 14.21.2.1. Effects of ethanol on the solubilities of selected organic compounds, (a) benzene, naphthalene, biphenyl, O anthracene, A benzo(a)pyrene, A perylene, O chrysene (b) hydantoic acid, hydantoin, O methyl hydantoic acic, O 5-ethyl hydantoin, A 5-isobutyl hydantoin (c) triglycine, O diglycine, A glycine [Adapted, by permission, from Li and YaUcovsky,/. Pharm. Set, 83, 1735 (1994).]...

The analogous N-thiocarboxyanhydrides have now been investigated. It was hoped that these thiocarbamates would be more stable to side reactions below pH 11 (decarboxylation) and those above pH 11 (NCA hydrolysis and hydantoic acid formation). While the His-NTA and those of Gly and Ala did prove more useful than the corresponding NCA in each case, the usefulness of the NTA derivatives was found limited by epimer formation of up to 20%. "... 

Hydantoic Acid Carbamylgdydne, ureido-acetic acid, glycoluric acid, N-carboxymethylurea) HjN-CO-NH-CHj-COOH CgHeOaNj MW, 118... 

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