2.4- Dihydroxy-pyrimidine

There are several other specialized ways to make individual amides but none is general. A random example is the self-condensation of malondiamide to give 4,6-dihydroxy-pyrimidin-2-ylacetamide (56JCS2312). 

Pyrido[3,2-d]pyrimidine, 6,7-dihydroxy-synthesis, 3, 227 Pyrido[3,2-(i]pyrimidine, halo-reactions, 3, 214... 

Pyrimido[5,4-d]pyrimidine, 4-amino-2,8-dihydroxy-3,8-disubstituted synthesis, 3, 365... 

Tanner,from infrared spectral work, tentatively concluded that 4,6- and 4,5-dihydroxy- and 4,5,6-trihydroxy-pyrimidines exist in the monooxo forms 117, 118 (X = H), and 118 (X — OH), respectively these conclusions are supported by ultraviolet spectral data and chemical evidence. " 2,4,5,6-Tetrahydroxypyrimidine has been isolated in two forms—dialuric acid and isodialuric acid, usually formulated as 119 and 120, respectively, on the basis of rather convincing chemical evidence [for a review see reference 109(f) cf. reference 178]. Isodialuric acid is converted into dialuric acid by base as would be expected if structures 119 and 120 are correct. On the basis of its infrared spectrum, dialuric acid has been concluded to exist in the tetrahydroxy form, but the correctness of this conclusion appears very doubtful. 

Methylpyrimidine has been obtained by the present method2 and by a three-step method that begins with the condensation of acetoacetic ester with urea to give 2,6-dihydroxy-4-methyl-pyrimidine the latter is treated with phosphorus oxychloride to give 2,6-dichloro-4-methylpyrimidine, which is reduced by zinc dust and water 8 or by catalytic hydrogenolysis.4... 

Likewise, l-[4-methylbenzyl]-4,7-dihydroxy-l,2,3-triazolo[4,5-d]pyridazine 275 reacts with phenylhydrazine, HMDS 2, and (NH4)2S04 to give the monoamino product 276 in 60% yield [83]. Reaction of l-benzyl-3-n.-butyl-4-hydroxy-l,2,3-triazo-lo[4,5-d]-pyrimidine 277 for 8 h at 120°C with cyclopentylamine, HMDS 2, and (NH4)2S04 affords the aminated product 278 in 49% yield [84] (Scheme 4.33). 

Other degradation products of the cytosine moiety were isolated and characterized. These include 5-hydroxy-2 -deoxycytidine (5-OHdCyd) (22) and 5-hydroxy-2 -deoxyuridine (5-OHdUrd) (23) that are produced from dehydration reactions of 5,6-dihydroxy-5,6-dihydro-2 -deoxycytidine (20) and 5,6-dihydroxy-5,6-dihydro-2 -deoxyuridine (21), respectively. MQ-photosen-sitized oxidation of dCyd also results in the formation of six minor nucleoside photoproducts, which include the two trans diastereomers of AT-(2-de-oxy-/j-D-eryf/iro-pentofuranosyl)-l-carbamoyl-4 5-dihydroxy-imidazolidin-2-one, h/1-(2-deoxy-J8-D-crythro-pentofuranosyl)-N4-ureidocarboxylic acid and the a and [5 anomers of N-(2-deoxy-D-eryfhro-pentosyl)-biuret [32, 53]. In contrast, formation of the latter compounds predominates in OH radical-mediated oxidation of the pyrimidine ring of dCyd, which involves preferential addition of OH radicals at C-5 followed by intramolecular cyclization of 6-hydroperoxy-5-hydroxy-5,6-dihydro-2 -deoxycytidine and subsequent generation of the 4,6-endoperoxides [53]. 

This enzyme [EC 2.5.1.9] catalyzes the conversion of two 6,7-dimethyl-8-(l-D-ribityl)lumazine to produce riboflavin and 4-(l-D-ribitylamino)-5-amino-2,6-dihydroxy-pyrimidine. 

Mit Diazonium-Salzen kuppeln in 4-Stellung 2-Aryl-5,6-dihydroxy-pyrimidine (2-Aryl-... 

Pol y-(3 1-u r i dyl i c acid), AP56 Potassium cumyl ide, AP T, AP62 Potassium 7-imidazo[4,5-d]-pyrimid1ne 6-suIfinite, AD65 Potassium 7-imidazo[4,5-dQ-pyrimidine 6-sulfonate, AD66 Potassium 5-nitro-2,6-dihydroxy-... 

Dihydroxy-4//-pyrido[l,2-a]pyrimidin-4-one 334 was obtained, when dibenzyloxy derivatives 333 were hydrogenated in dimethylform-amide in the presence of yV-methyl-TV-trimethylsilyl trifluoroacetamide. Dihydroxypyrido[l, 2-a]pyrimidin-4-one334 was then reacted, without isolation, with (Z)-2-amino-a-[(2-diphenylmethoxy)-l, l-dimethyl-2-oxoe-... 

Ethyl 3-(7-bromomethyl-4-oxo-4//-pyrido[ 1,2-a]pyrimidin-3-yl)propio-nate reacted with 2,4-dihydroxy-3-propylacetophenone in boiling methyl... 

Reaction of 9-bromomethyl-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-3-carboxylates 505 and their homologs with 2,4-dihydroxy-3-propyl-and -3-allyl-acetophenone 506 in boiling methyl ethyl ketone in the presence of potassium carbonate afforded 9-(4-acetyl-3-hydroxy-2-substituted phenoxymethyl) derivatives (507) [87EUP242230 88JAP(K)88/246375]. 

Almost all of the syntheses of (25) involve condensation of 2,4,5,6-tetraamino-pyrimidine with dihydroxy acetone [41]. This condensation, however, also yields varying amounts of 2,4-diamino-6-methylpteridine, as well as the 7-sub-stituted regioisomers of both the hydroxymethyl and methyl compounds separation of pure, isomer-free (25) from the resulting mixture is a formidable undertaking. Despite various claims that subtle adjustments of pH, or the presence or absence of various buffers, favour formation of the desired... 

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