Parabanic acid derivatives

Parabanic acid derivatives 706 are obtained in the reaction of carbodiimides with oxalyl chloride. ... 

Photolysis of 1,3-dimethylimidazolidinetriones (parabanic acid derivatives) in the presence of alkenes in benzene solution results in the formation of spiroketones (141). In protic solvents, however, solvent is incorporated into the products (Scheme 72) <89JOC2359>. 

Further treatment with p-methoxyphenyl magnesium chloride provided a protected a-amino ketone intermediate (in a yield of 62%) that could be het-erocyclized with cyanamide and subsequently reduced to provide the 4,5-dibenylated imidazole (86% over two steps). Treatment with a TMS-protected parabanic acid derivative furnished naamidine A in a yield of 80%. 

Imino derivatives 100 of compounds of type 95 were also directly prepared from cumulated ylides 82 or 4 and parabanic acid derivatives 99 by a presumed mechanism as depicted in Scheme 22 [70]. Attack of the nucleophilic ylidic carbon atom at the most electrophilic amide-type carbonyl carbon atom, ring opening with loss of phenyl isocyanate, and recyclization by N-C bond formation are the key steps. This reaction is reminiscent of an older one, furnishing 5,5-diethoxy- l-thiobenzoyl-4-triphenylphosphoranylidene-pyrrolidine-2,3-dione 102 from 2-phenylthiazoHne-4,5-dione 101 and 4 [71] in modest yield. 

Vialas C, Claparols C, Pratviel G () Meunier B (200) Guanine oxidation in double-stranded DNAby Mn-TMPyP/KHS05 5,8-dihydroxy-7,8-dihydroguanine residue as a key precursor of imidazolone and parabanic acid derivatives. J Am Chem Soc 122 2157-2167... 

Alloxan forms an oxime (1007) which is the same compound, violuric acid, as that formed by nitrosation of barbituric acid likewise, a hydrazone and semicarbazone. Reduction of alloxan gives first alloxantin, usually formulated as (1008), and then dialuric acid (1004 R = OH) the steps are reversible on oxidation. Vigorous oxidation with nitric acid and alkaline hydrolysis both give imidazole derivatives (parabanic acid and alloxanic acid, respectively) and thence aliphatic products. Alloxan and o-phenylenediamine give the benzopteridine, alloxazine (1009) (61MI21300). 

Fig. 11. Mechanism for formation of parabanic acids from the methylated uric acid-4,5-diol derived from theobromine (3,7-dimethylxanthine) and caffeine (1,3,7-trimethylxan-thine). Molar amounts of products are those formed in 1 M HOAc...

Oxidation of xanthine or uric acid derivatives with chromic acid gives the appropriate alloxane and urea as primary products which undergo further oxidation to corresponding parabanic acids (imidazolidine-2,4,5-triones) and purpuric acids which, on addition of ammonia, constitute the murexide test. This is positive for all purines capable of oxidation to an alloxane derivative, For a review see ref 48. 

Lithiation at the C2 position of the imidazole ring by means of n-BuLi was followed by a treatment with tosyl azide which furnished the corresponding 2-azido imidazole in a yield of 89%. This azido group was reduced to an amino group with palladium on carbon under hydrogen atmosphere (in a yield of 95%). Finally, the 2-aminoimidazole was treated with a TMS-activated derivative of parabanic acid, a reaction that afforded the target molecule naa-midine G in a yield of 78%. This eight-step synthesis provided naamidine G in a total yield of (95 x 97 x 85 x 98 x 81 x 89 x 95 x 78) 41%. 

After the research of Wohler and Liebig (1838, see p. 333), uric acid and its derivatives were investigated by Schlieper. The latter showed that uric acid on reduction by hydriodic acid forms glycocoll and the decomposition products of urea (NH3 and CO2). Gerhardt formulated alloxan as the mesoxalyl, and parabanic acid as the oxalyl, derivatives of urea, which he then regarded as hydrate d oxyde de cyanammonium , giving complicated formulae, which were simplified by Kekule as ... 

Partial and selective cleavage of isopropylidene derivatives of carbohydrates with subsequent 0-acyl group migration s. 14, 19 Preferential and selective cleavage of benzylidene derivatives of carbohydrates s. 14, 20 Parabanic acids from 5,5-dialkoxyhydantoins s. 14, 21... 

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