Ureide synthesis

In more recent experiments in which the unidentified compound has been detected, it has coelectrophoresed with the ureide, allantoic acid (Figure 8). Allantoin, which is a precursor of allantoic acid in the purine degradation pathway of ureide synthesis, was not labeled significantly. 

Paulus, W. and Genth, H., 1980. N-Aryl-N -acryloyl-ureides, synthesis and application as microbicides. EP 0023 976 BI. 

In a modification of the original method. Read (60) replaced a-amino acids with a-amino nitriles. This reaction is sometimes known as Strecker hydantoin synthesis, the term referring to the reaction employed for the synthesis of the a-amino nitrile from an aldehyde or ketone. The cycli2ation intermediate (18) has been isolated in some cases (61), and is involved in a pH-controUed equiUbrium with the corresponding ureide. 

Forty years after the initial proposal, Sweet and Fissekis proposed a more detailed pathway involving a carbenium ion species. According to these authors the first step involved an aldol condensation between ethyl acetoacetate (6) and benzaldehyde (5) to deliver the aldol adduct 11. Subsequent dehydration of 11 furnished the key carbenium ion 12 which was in equilibrium with enone 13. Nucleophilic attack of 12 by urea then delivered ureide 14. Intramolecular cyclization produced a hemiaminal which underwent dehydration to afford dihydropyrimidinone 15. These authors demonstrated that the carbenium species was viable through synthesis. After enone 13 was synthesized, it was allowed to react with N-methyl urea to deliver the mono-N-methylated derivative of DHPM 15. 

D-p-Hydroxyphenylglycine is an important component of certain semi-synthetic antibiotics such as the semi-synthetic cephalosporins cefadroxil and cefatrizine and the semi-synthetic penicillin amoxicillin, with a combined world market in excess of 3 x 10 /a. Synthesis was possible from DL-5-monosubstituted hydantoins (cyclic ureides of amino acids) provided that a selective D-hydantoinase could be found, which would be competitive with chemical methods. 

To determine whether xylose parallels the behavior of glucose in reacting to form ureides and other products, analyses were done on samples taken from a previous synthesis. That synthesis, using xylose and P/C/U/F molar ratios of 1 1 0.5 2.5, had yielded a strong resin (experiment 16 in references 9,10),... 

Reductive desulfurization in the synthesis of cyclic ureides and lactams 88MI17 90MI13. 

Sonne, J. C., Buchanan, J. M., and Delluva, A. M., Biological precursors of uric acid I. The role of lactate, acetate, and formate in the synthesis of the ureide groups of uric acid. J. Biol. Chem. 173, 69-79 (1948). 

Johnson and Bergmann, as well as Helferich and Kosche, noted the possibility that the glycosyl ureides might be utilized as intermediates for an improved method of synthesis of pyrimidine nucleosides. Fischer s method was used for obtaining 1-n-glucosylurea as well as 1-n-arabinosyl-urea and 1,3-di-n-xylosylurea. 

Whether the glycosyl ureides play a role in normal metabolic processes remains a challenging question. The fact that the chemical synthesis of pyrimidine nucleosides from glycosyl ureides has been demonstrated should serve to stimulate further investigation of this problem, particularly with the application of some of the more recent, sensitive techniques including radioactive tracers and paper chromatography. ... 

Figure 9. Reactions of purine ca-tabolism implicated in the synthesis of ureides...

Balance sheets for production, storage, and utilization of ureides have been constructed for different stages of development of the nodulated cowpea (Herridge et al., 1978). In practically all periods of growth the shoot metabolized over 90% of the ureides it received from the roots, which acted as a N source for protein synthesis. During early fruit development when N... 

Ureides are metabolized by conversion to urea and glyoxylate as shown in Fig. 6. Allantoin may be hydrolyzed to allantoic acid as discussed above. The key enzyme in the breakdown is allantoicase, which is located in the shoots and pods (Tajimaet al., 1977). Such a system allows for the transport of N from the nodule to the shoot and rapid metabolism of the ureides to liberate N for protein synthesis (Herridge et al., 1978). 

An MS investigation of the three-component base-mediated Biginelli synthesis of dihydropyrimidines has found evidence for a hemiacetal intermediate (117), but no sign of a bis-ureide (118). ° A prolinamide gives up to 99% ee in Biginelli cyclocondensations of urea, aldehyde, and ethyl acetoacetate. ... 

The corresponding reaction with 2-methylamino-5-nitroaniline affords an unambiguous synthesis of l-methyl-6-nitroquiuoxalin-2-one, the A -methyl derivative of (6) this product is also obtained by treatment of (6) with methyl iodide and methanolic sodium methoxideA Condensation of o-phenylenediainine or. V methyl-o-phenylcne-diamine with alloxan (8) in neutral solution gives the ureides (9) and (10), respectively. However, reaction of o-phenylenediamine with 1,3-dimethylalloxan (13) yields quinoxalin-3-one-2-carboxymethyl-amide (14), rather than the dimethyl ureide. Methylation of (9) in acetone in the presence of potassium carbonate gives the spiro-hydantoin (11). 

In the mechanism of the Biginelli synthesis [265], the rate-determining step is the acid-catalyzed formation of an acylimine 35 from aldehyde and urea. By N-protonation (or metal-N-coordination), the imine 35 is activated (as an iminium ion) and intercepted by the P-ketoester (as enol or metal enolate) to give rise to an open-chain ureide 36, which subsequently cyclizes (via the cyclic ureide 37 and its dehydration) to afford the dihydropyrimidinone 33. Biginelli compounds of type 33 have been synthesized independently in multistep sequences [266]. 

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