References pyrimidines

SCHEME 25.5(B) Microwave-assisted solvent-free trimerization of aliphatic nitriles to pyrimidines (Reference 54). 

Nucleic acids are acidic substances present m the nuclei of cells and were known long before anyone suspected they were the primary substances involved m the storage transmission and processing of genetic information There are two kinds of nucleic acids ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) Both are complicated biopolymers based on three structural units a carbohydrate a phosphate ester linkage between carbohydrates and a heterocyclic aromatic compound The heterocyclic aro matic compounds are referred to as purine and pyrimidine bases We 11 begin with them and follow the structural thread... 

Since IR spectra are essentially due to vibrational transitions, many substituents with single bonds or isolated double bonds give rise to characteristic absorption bands within a limited frequency range in contrast, the absorption due to conjugated multiple bonds is usually not characteristic and cannot be ascribed to any particular grouping. Thus IR spectra afford reference data for identification of pyrimidines, for the identification of certain attached groups and as an aid in studying qualitatively the tautomerism (if any) of pyrimidinones, pyrimidinethiones and pyrimidinamines in the solid state or in non-protic solvents (see Section 2.13.1.8). 

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. 

Early reports of analgesic and antiarthritic activity in octahydropjTido[4,3-d]pyrimidines do not appear to have been substantiated, but a number of recent patents refer to the antipyretic, diuretic, bacteriostatic, sedative, and coronary-dilating activities of a series of 5,6,7,8-tetrahydropyrido[4,3-d]pyrimidines. Pharmacological properties claimed for, 5,6-dihydropyrido[2,3-[Pg.198]

Substituted pyrimidine Quaternizing reagent Position of quaternization Principal Subsidiary product product Reference... 

Tliis is one of the most actively developing and closely watched fields of heterocyclic tautomerism—only the study of purines and pyrimidines is of comparable contemporary interest. Tire number of references is so high that many relevant works have had to be neglected, whereas in other sections of this chapter relatively minor contributions have been commented on because they pertained to a field where few contributions are available. Tire selection criteria were (1) all pertinent authors are quoted at least once, (2) full papers are preferred to communications or letters, and (3) recent works are preferred to earlier ones because they usually quote the previous publications. 

Finally, Katritzky et al.sii have measured first-order rate coefficients for deuteration of pyrimidines by deuterated sulphuric acid (Table 152), and all pD and —D0 values given in the Table refer, as in the earlier work, to a temperature of 20 °C. For 2-aminopyrimidine, reaction clearly occurs on the free base and comparison of the data with the earlier work on anilines and by making a number of assumptions, conjugate acid at higher acidities is apparent and this follows the previously established pattern. This work yielded a value of 0.55 for [Pg.236]

The Chemistry of Heterocyclic Compounds has been published since 1950 under the initial editorship of Arnold Weissberger, and later, until his death in 1984, under the joint editorship of Arnold Weissberger and Edward C. Taylor. In 1997, Peter Wipf joined Prof. Taylor as editor. This series attempts to make the extraordinarily complex and diverse held of heterocyclic chemistry as organized and readily accessible as possible. Each volume has traditionally dealt with syntheses, reactions, properties, structure, physical chemistry, and utility of compounds belonging to a specihc ring system or class (e.g., pyridines, thiophenes, pyrimidines, three-membered ring systems). This series has become the basic reference collection for information on heterocyclic compounds. 

The inverse electron demand reactions of 2,4,6-tris(ethoxycarbonyl)-1,3,5-triazine and 5-aminopyrazoles to provide a one-step synthesis of pyrazolo[3,4-. 

The double-stranded structure of DNA can be separated into two component strands (melted) in solution by increasing the temperature or decreasing the salt concentration. Not only do the two stacks of bases puU apart but the bases themselves unstack while still connected in the polymer by the phosphodiester backbone. Concomitant with this denaturation of the DNA molecule is an increase in the optical absorbance of the purine and pyrimidine bases—a phenomenon referred to as hyperchromicity of denaturation. Because of the... 

Molecular rotors with a dual emission band, such as DMABN or A/,A/-dimethyl-[4-(2-pyrimidin-4-yl-vinyl)-phenyl]-amine (DMA-2,4 38, Fig. 13) [64], allow to use the ratio between LE and TICT emission to eliminate instrument- and experiment-dependent factors analogous to (10). One example is the measurement of pH with the TICT probe p-A,A-dimethylaminobenzoic acid 39 [69]. The use of such an intensity ratio requires calibration with solvent gradients, and influences of solvent polarity may cause solvatochromic shifts and adversely influence the calibration. Probes with dual emission bands often have points in their emission spectra that are independent from the solvent properties, analogous to isosbestic points in absorption spectra. Emission at these wavelengths can be used as an internal calibration reference. 

Intramolecular inverse electron-demand Diels-Alder reaction of iV-propargyl-2-(pyrimidin-2-yl)pyrrolidine provides an alternative route to pyridopyrrolizines. For example, heating of 130 to 170 °C in nitrobenzene affords the cyclized product with the loss of HCN <1992JOC3000> (Equation 9). The above reference includes molecular orbital (MO) calculations on relative reactivities in this series. 

Nucleophilic substitution of leaving groups is probably the most important area in pyrimidine reactivity and, in particular, the differential reactivity of C-2 and C-4 is the most investigated topic. The displacement of 2- and 4-sulfide and sulfone groups is referred to in the synthesis section. The selective hydrolysis of 4-amino-2-chloropyrimidines under acidic conditions has been studied in great detail by a process research group <06OPRD921>. 

In such names, numerals will refer to carbon atoms of the sugar moiety, and primed numerals to the positions on the nitrogenous base compare Ref. 1, pp. 200 and 208. Pyrimidines and purines are numbered by the Chem. Abstracts system. 

Figure 3.4 The five bases found in nucleic acids may be categorized as either pyrimidines or purines. Refer to text for details...

The P-site of adenylyl cyclase inhibits cyclic AMP accumulation. Since P, and P2 receptors are located on the cell surface, they bind purines or pyrimidines in the extracellular space. There also is an adenosine binding site located intracellularly on the enzyme adenylyl cyclase (see Ch. 21). This is referred to as the P-site of adenylyl cyclase. Binding of adenosine and other purines, notably 3 AMP, 2 deoxy-3 -ATP and 2, 5 -dideoxyadenosine to this site, inhibits adenylyl cyclase activity [8]. The P-site of adenylyl cyclase and other intracellular purine binding sites are not classified as purinergic receptors. 

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. 

We should note at this point that the TCA cycle is more than just a means of producing NADH for oxidative phosphorylation. The pathway also provides a number of useful intermediates for other, often synthetic, pathways. For example, citrate is the starting substance for fat synthesis (Chapter 9) succinyl-CoA is required for haem production and 2-oxoglutarate and oxaloacetate in particular are involved with amino acid and pyrimidine metabolism. Pathways which have dual catabolic/anabolic functions are referred to as amphibolic . 

Numerous publications on uracil and thymine and their role in controlling the metabolism, reproduction, and growth of living systems — in particular in the transcription of genetic information and biosynthesis of proteins — have already appeared in the literature. Therefore, these two important pyrimidines will not be discussed again in the present review. Some pertinent literature references are provided [244—264]. 

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