Pyrimidine composition

Wyatt, G.R. The purine and pyrimidine composition of deoxypentose nucleic acids. Biochem. J. 48, 584-590 (1951)... 

Purine and Pyrimidine Composition of Deoxyribonucleic Acid from Bacteriophages,... 

X-Ray analyses and solid-state IR spectra were recorded for a number of 1,4-and 1,6-dihydropyrimidines, demonstrating the dependency of the tautomeric composition in the crystal on the substitution in the pyrimidine ring and on the ability of these compounds to form intermolecular hydrogen bonds. Thus,... 

Figure 2. Structures of phthalazine (32,33), pyrimidine (34,35), and indoline (36,37) ligands used in the Sharpless AD and composition of AD-mix a and AD-mix p.

The relative numbers of these pyrimidine dimers formed depend upon the nucleotide composition of the DNA. Setlow and Carrier examined dimer formation in DNA from three microorganisms whose DNA had differing A-T contents. The composition of the DNA, and... 

The close correspondence of the DNA absorption spectrum with that of a mixture of mononucleotides of the same composition illustrates the weak nature of the interactions between neighboring purine and pyrimidine bases guanine (G), cytosine (C), adenine (A), and thymine (T) at an interplanar separation of 3.36 A in the unexcited double-helical configuration. On the other hand the structureless fluorescence band of (calf-thymus) DNA is red-shifted by 3500 cm-1 from the fluorescence spectral origin of the mononucleotides it closely resembles the fluorescence spectrum of the dinocleotide ApT (and of poly dAT) and is accordingly identified131 with the fluorescence... 

In contrast, some substituted anilines, e.g. 2-nitroaniline,143 2-chIoro-4-(trifluoromethyI)ani-Iine,143 benzene-1,3-diamine,150 or 4-chlorobenzene-1,3-diamine,150 give only very low yields of product or formed tars under the fluorination conditions. The diazotization followed by in situ fluorodediazoniation of the corresponding diazonium salts have been systematically studied in hydrogen fluoridc/base solutions of different composition to ascertain the most important influences on the reaction.329 Besides numerous examples of substituted anilines, various derivatives of pyridine, pyrimidine, 1.3,5-triazine, and benzthiazole have been included in these investigations (yields 45—99%). 

Kato et al.19 compared the mass spectra of 2-methyl-4-oxo-4/7- and 4-methyl-2-oxo-2//-pyrido[l,2-a]pyrimidines. Fragments at m/e = 120 and 92 appeared only in the spectrum of the 2-oxo isomer. In the spectrum of the 4-oxo isomer the peak at m/e = 105 corresponds to a single fragment of composition C6H5N2, whereas for the 2-oxo isomer, it is a mixture of two fragments, C6H5N2 and C7H7N. 

Increasing the electron-donor properties of the R, substituent in the case of dihydro derivatives of 1,2,4-triazolo[l, 5-a]pyrimidines [X, Z are N, Y is C(R)], tetrazolo[l, 5-a]pyrimidines (X, Y, Z are N), and pyrimidofl, 2-a]benzimidazoles (X, Y are o-C() I4, Z is N) tends to stabilize the B form. This can be explained by the conjugation of Rj with the electron-withdrawing azomethine group and the azole moiety. Reduction of the electron-accepting properties of the azole fragment (imidazopyrimidines and pyrazolopyrimidines) decreases the influence of the Ri substituent on tautomeric composition. 

Dichloroacetyl)-3,3,9a-trimethylperhydropyrido[ 1,2-u]pyrimidin-6-one was applied in herbicidal compositions as a sefaner (99EUP901752). 

Another example is the photoreaction of tctrazolo[ 1,5- ]pyrimidinc 14 with aromatic compounds in the presence of trifluoroacetic acid (TFA) to give 2-(2-, 3-, and 4-substituted anilino)pyrimidines together with 2-aminopyridine and biphenyl or diarylmethanes. Here the key intermediate is also the 2-pyrimidylnitrenium ion originating from the photochemical decomposition of an imidoyl azide. This ion, depending on the reaction conditions, is present either in the singlet or triplet state and this governs the composition of the products (Scheme 11) <1998JP0478>. 

Although blues prepared from unsubstituted uracil, thymine and related bases (e.g., 6-methyluracil, 5,6-dihydrouracil etc.) were the first to be prepared and tested, their composition is the least clear. The author suspects that there is still long way to go to fully understand the nature of these blues . It is possible that there are even blues built on different principles. A main obstacle to the elucidation of Pt blues derived from the unsubstituted pyrimidine nucleobases lies in their versatility as ligands. Not only is there the possibility that these ligands bind to metal ions, specifically Pt, via N(l) or N(3) or (only with uracil) C(5), but also many possible combinations of two or more binding sites, e.g., N(l),0(2) N(3),0(2) N(3),0(4) N(1),N(3) N(3),0(2),0(4) N(1),0(2),N(3),0(4) etc. (Scheme 6). A series of these binding patterns has been established by X-ray crystal-structure analyses [68-70], and others are likely on the basis of spectroscopic studies [71] [72] or from comparison with results obtained for N(l) substituted derivatives. The possibility of different tautomers of platinated forms being... 

Despite some indisputable progress in the understanding of the nature and composition of platinum blues derived from m-(NH3)2P(" which has been achieved within the last twenty years, in particular thanks to X-ray crystallography, there is still no comprehensive picture available on the -blues . This is true in particular for the platinum pyrimidine blues , on which this review had focused. The amorphous nature of these materials has restricted the methods of investigation to questions such as metal-metal separations [97] or delocalization of spins due to the presence of Ptm centers in a Pt chain [29] [51]. These methods have, however, not provided insight... 

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