Pyrimidines alloxan

The highly oxidized pyrimidine alloxan also gives a semiquinone (117) ... 

Alloxan (1003) has been observed in the mucus associated with dysentery and it was the very first pyrimidine made synthetically when Brugnatelli oxidized uric acid in 1818. Alloxan has an interesting diabetogenic action which appears to be associated with removal of essential zinc from insulin by chelation. Such permanent diabetes may be induced in fish, dogs, cats, sheep, some birds, monkeys and other creatures, but not in man, owls or guinea-pigs certain pyrimidines related to alloxan show some such activity. 

Alloxan [2,4,5,6(l//,3//]pyrimidine, tetrone] [50-71-5] M 142.0, m 170 (dec), pK 6.64. Crystn from water gives the tetrahydrate. Anhydrous crystals are obtained by crystn from acetone, glacial acetic acid or by sublimation in vacuo. 

The unlikely transformation of a pyrimidine into a quinoxaline has, indeed, been reported. Thus 4,5-dimethyl-1,2-benzenediamine (402) and alloxan (403, R = H) under acidic conditions gave 6,7-dimethyl-3-ureidocarbonyl-2(17/)-quinoxalinone (404, R = H) ( 30% see original for details) A(-methylalloxan (403, R = Me) likewise gave 6,7-dimethyl-3-(A(-methylureido)carbonyl-2(17/)-quinoxalinone (404, R = Me) in 50% yield.Such condensations gave improved yields under solid-state conditions. 

The most important pyrimidine derivatives are those upon which biological organisms depend. Cytosine 1018 and uracil 1019 are found in ribonucleic acid (RNA) in the form of their ribonucleotides, cytidine 1020 and uridine 1021, while in deoxyribonucleic acid (DNA), cytosine and thymine 1022 are found in the form of their 2 -deoxyribonucleotides, 2 -deoxycytidine 1023 and thymidine 1024. 5-Methylcytosine 1025 is also found to a small extent (c. 5%) in human DNA in the form of its 2 -deoxyriboside 1026, and 5-(hydroxymethyl)cytosine-2 -deoxyriboside 1027 has also been detected in smaller amounts <2005CBI1>. Many variants of cytosine and uracil can be found in RNA including orotic acid 1028 in the form of its ribonucleotide orotidine 1029. Other pyrimidine derivatives to have been isolated from various biological sources include 2 -deoxyuridine 1030, alloxan 1031, and toxopyrimidine (pyramine) 1032 (Figure 2). 

Methylene derivatives formed from alloxan can serve as bis-electrophiles and react with species such as guanidine to give pyrimido[4,5-tf pyrimidines directly (Equations 91 and 92). Formation of the Michael acceptor and the corresponding cyclization with thiourea can be carried out either in a single step (Equation 93) <2003RCB2457> or with isolation of the intermediate (Scheme 58) <2003SC3747> in either case, the process is reported to proceed most efficiently in the solid state under microwave irradiation. 

Pyrimidine is a six-membered aromatic heterocyclic compound that contains two nitrogen atoms, separated by a carbon atom, in the ring. Nucleic acids, DNA and RNA, contain substituted purines and pyrimidines. Cytosine, uracil, thymine and alloxan are just a few of the biologically significant modified pyrimidine compounds, the first three being the components of the nucleic acids. 

Alloxan or N,N-Mesoxalyl Urea (Pyrimidine-tetrone or Erythric Acid of Brugnatelli, OC-NH-CO... 

Some pyrimidine derivatives, such as alloxan, react in the absence of mineral acid with 3,4-diaminopyridines to give hydantoins through a ureide93 in analogy to the cyclization of 1,4,5-triazanaphthalenecarboxy ureides.94... 

A photophysical study of the interaction of 2-amino-4,6-dimethylpyrimidine in p-CD has been carried out. Calculations have been carried out in an examination of the isomerism of methyl urocanate. Density functional theory techniques have been used to study the dimerization of thymine units in DNA. The effects of both low intensity irradiation (254 nm) or laser photolysis at 266 nm on adenosine have been reported. The photoionization of various purine and pyrimidine derivatives can be brought about by 266 nm nanosecond laser photolysis. Irradiation of alloxan in the presence of alkenes with allylic hydrogens affords adducts of 5-hydroxy-5-alkenyl barbituric acid. When the alkene is... 

Pteridines may also be constructed from pyrimidines which are 4-(substituted)amino-5-unsub-stituted, from pyrimidine-4,5-diones (e g., alloxane), and front 5-halo-4-oxo-, 5-halo-4-amino-, or from 4,5-dihalopyrimidines. 

The ready availability of alloxazines from reaction of 0-phenylenediamine hydrochlorides and alloxan makes them attractive starting materials for the preparation of quinoxaline-2-carboxylic acids. When the pyrimidine ring of the alloxazine is cleaved with ammonia, a 3-... 

AI3-15282 Alloxan Alloxan 7169 Alloxane Barbituric acid, 5-oxo- EINECS 200-062-0 Mesoxalylcarbamide Mesoxalylurea NSC 7169 2,4,5,6-Pyrimidintetron 2,4,5,6(1H,3H)-Pyrimidine-tetrone 2,4,5,6-Tetraoxohexa-hydropyrimidine Urea, mesoxalyl-. Used in nutrition experiments. Causes diabetes in experimental animals. Crystals dec 256° soluble in H2O. Wako Pure Chem. Ind. 

Alloxan 29 is formed in organisms by the oxidative degradation of uric acid (see p 414). Willardiin 30 is a nonproteinogenic a-amino acid with a uracil structure which is present in the seeds of some types of acacia. A few pyrimidine antibiotics, especially those isolated from streptomyces, possess potent antitumour properties, e.g. the structurally complex bleomycins 31. The commercial product is a mixture of various bleomycins, main components being bleomycins A2 (55-70%) and B2 (25-32%). 

These results drew attention to a reaction studied by Biltz and Kramer in 1924, the general applicability of which, however, was not recognized for 50 years These authors studied the reaction of ethyl diazoacetate with the tetrahydrate of pyrimidine-2,4,5,6-tetrone (9.11, alloxane) and found the addition product 9.12 (9-10). 

It was naturally tempting to think that dehydroascorbic acid might have a specific role in the production of experimental diabetes, perhaps even in the human disease. Ever since alloxan diabetes was first described there has been an understandable tendency to guess that some alloxanlike metabolite, or even alloxan itself, might account for beta cell failure in human diabetes. Its close chemical relation to the pyrimidines— present in all nucleic acids, but whose metabolic pathways are at present mysterious—make this an intriguing possibility. Now dehydroascorbic acid is added to the list of diabetogenic suspects. 

H,3H)-Pyrimidinedione, 5-chloro-3-(1,1-dimethylethyl)-6-methyl-. See Terbacil 5-Pyrimidinemethanol, a-(2-chlorophenyl)-a-(4-chlorophenyl)-. See Fenarimol Pyrimidine phosphate. See Pirimiphos-methyl, Pyrimidinetetrone hydrate 2,4,5,6(1H,3H)-Pyrimidinetetrone hydrate. See Alloxan monohydrate... 

In the first place, at least one of the purines, uric add (II), is predicted to be an exceptionally good electron donor. On the other hand barbituric acid (III) and alloxan (IV) although playing a role in the biochemistry of the pyrimidines similar to the one played by uric acid in the biochemistry of the purines, are predicted to be particularly poor electron donors. In fact, alloxan is even predicted on the basis of this type of calculation to be rather an electron acceptor and a better one than the bases of the nucleic acids. 

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