Pyrimidines 4-amino- from

Table 22 Various ring-closure reactions to [1,2,4]triazolo[1,5-a]pyrimidines starting from 3-amino[1,2,4]triazoles...

The synthetic pathway to tetrazolo[l,5-tf]pyrimidines starting from 5-amino-tetrazoles has already been discussed in CHEC-II(1996) <1996CHEC-II(8)465>. During the recent period of time, several modifications of this approach have been described. The obtained products - among them some partly saturated derivatives - and the applied reagents as well as yields and references are summarized in Table 9. 

Treatment of the symmetrical triaminopyrimidine (50-1) with sulfuryl chloride ties up the two adjacent amines in a thiadiazole ring, protecting those groups from attacks in subsequent reactions. Reaction of the product (50-2) with ortho difluorinated benzylamine (50-3) results in the replacement of the pyrimidine amino group by that in the reagent most hkely by an addition-elimination sequence to afford (50-4). That amino group is then converted to the formamide (50-5) with formic acid. Exposure of the product to Raney nickel leads to a loss of sulfur and the formation of the transient intermediate (50-6). This cyclizes to a purine... 

From purines and pyrimidines In the catabolism of purines ad pyrimidines, amino groups attached to the rings are released as ammonia. 

Phosgenimium chlorides (585) permit a regiospecific synthesis of 3-(di-substituted amino)triazolo[4,3-c]pyrimidines (588) from the 4-hy-drazinopyrimidine 488 without a Dimroth type of rearrangement... 

It was not possible to reverse the above sequence of reactions i.e., to annulate the pyrimidine ring from (627) and then to form the peptide linkage (which would have given an optically active product) because of the extraordinary insolubility of 5-deaza-7,10-ethano-4-amino-4-deoxypteroic acid... 

Each of the diazines can be constructed from an appropriate source of two nitrogens and a dicarbonyl compound. In the case of pyridazines, the nitrogen source is, of course, hydrazine and this in combination with 1,4-dicarbonyl compounds readily produces dihydro-pyridazines, which are very easily dehydrogenated to the aromatic heterocycle. Pyrimidines result from the interaction of a 1,3-dicarbonyl component and an amidine (as shown) or a urea (giving 2-pyrimidones) or a guanidine (giving 2-amino-pyrimidines), without the requirement for an oxidation step. 

The preparation of 2-amino-substituted 5-ethoxypyrido[4,3-d]pyrimidines with sodium ethox-ide in ethanol 532 or of 2-alkyl(aryl)-6-benzyl-4-butoxy-5,6,7,8-tetraliydropyrido[4.3-chloro compounds prepared in situ has been developed. An example starting from the isolated chloropyrido[4,3-d]pyrimidine is the preparation of 5-ethoxy-2,7-diphenylpyrido[4,3-d]pyrimidine (6) from the 5-chloro compound 5.527... 

Fusion of an o-aminonitrile with urea at 175°-200°C gives an annelated 4-aminopyrimidin-2-one, e.g., the quinolino[2,3-d]pyrimidine 123 from 2-amino-3-cyanoquinoline.117 The reaction is thought to pass through a ureide of the type 124. Because urea begins to self-condense to the biuret at... 

From the young pea seedlings of Pisum sativum L. var. Rondo there was isolated another pyrimidine amino acid, the structure of which was initially proposed [429] as L- -(5-uracilyl)alanine (LXXVIIIa). However, its physical constants by no means agree with those of the authentic -(5-uracilyl)alanine unequivocally synthesised earlier [430, 431]. The structure has since been revised to L- -(3-uracilyl)alanine (LXXIX, isowillardiine) by examination of its ultraviolet absorption characteristics and chemical reactions [422] and substantiation by infrared, NMR, and mass spectrometry [432]. Its biological role has not yet been determined. 

Van Gennip et al. (1991) contributed a chapter on the application of TLC and HPTLC for the detection of aberrant purine and pyrimidine metabolism in man. The authors provided extensive information on sample preparation of purines and pyrimidines, particularly from body fluids, blood, and tissue cells. The chapter is extensively illustrated with maps of two-dimensional chromatograms showing the positions of various purines and pyrimidines from normal and meta-bolically impaired subjects. Cserhati (1991) presented information on the retention behavior of some synthetic nucleotides, mainly 5-substituted deoxyuridine derivatives, on cyano (CN), diol, and amino (NH2) precoated HPTLC plates. Brown (1991) provided a review with many references on numerous methods, including TLC, useful for the separation and identification of purines, pyrimidines, nucleosides, and nucleotides. 

Ammonium hydroxide Pyrimidine nucleosides from carbohydrates and cyanoacetylenes via carbohydrate 2-amino-Zl -oxazoline ring... 

Generally used when ion exchange properties are not needed. Most often used for the separation of sugars, amino acids, and similar compounds. A popular sorbent for the separation of nucleic acid derivatives, it separates pyrimidines (faster from purines. Conunercial grade microcrystalline cellulose (Avicel) has been used for the retention of guanine (base or nucleoside) in either acid (HCI formic acid) or base (ammonia) solvents. 

Amino- from 4,6-dichloro- via 4-amino-6-chloro-pyrimidines... 

Amines from formamides s. 12,470 5-Amino- from 5-formamido-pyrimidines s. 14, 38 Selective hydrolysis s. 13, 44, 56 NGHO NH... 

Labeled compounds—5-Amino- from 5-nitroso-pyrimidines s. 12, 442 non-labeled compounds, also from malononitriles, ureas, and thioureas s. J. Da-voll, Soc. 1960, 131... 

Pyrimidine ring from guanidine with preceding replacement of hydroxyl by amino groups 5H-Pyrrolo[3,4-d]pyrimidine-7(6H)-ones... 

The other pyrimidines arise from the uridine derivatives. One enzyme converts the C-6 hydroxyl group of uridine triphosphate with the aid of ammonia or glutamine to an amino group. Uridine triphosphate thus becomes cytidine triphosphate. The transition to deoxyribose derivatives occurs at the level of the diphosphates... 

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