Mass spectrometric investigation of N-sulfonylated purine nucleic bases and nucleosides

The gas/phase behaviour of N-sulfonylated purine nucleic bases and nucleosides towards electron impact (EI) and matrix-assisted laser desorption/ionization (MALDI) occurring in a ion trap of a Fourier transform ion cyclotron resonance mass spectrometer is investigated. The influence of the storage time on the protonated molecule ([M+H](+)) abundance under EI conditions confirms that the formation of these ions proceeds through ion/molecule reactions. Using stored-waveform inverse Fourier transform (SWIFT) selective isolation of M(+.) or H(3)O(+), self-chemical ionization, M(+.)/M, and chemical ionization, H(3)O(+)/M, are detected. Investigation of specific EI expulsion of SO(2), SO(2)H and/or SO(2)H(2) from M(+.) and/or [M+H](+) shows that oxygen protonation in bond;SO(2)bond; proceeds faster than nitrogen protonation. Expulsion of SO(2) from molecular ions is not observed in MALDI mass spectra of nucleosides.     

Interaction of low-energy electrons with the purine bases, nucleosides, and nucleotides of DNA

The authors report results from computational studies of the interaction of low-energy electrons with the purine bases of DNA, adenine and guanine, as well as with the associated nucleosides, deoxyadenosine and deoxyguanosine, and the nucleotide deoxyadenosine monophosphate. Their calculations focus on the characterization of the pi* shape resonances associated with the bases and also provide general information on the scattering of slow electrons by these targets. Results are obtained for adenine and guanine both with and without inclusion of polarization effects, and the resonance energy shifts observed due to polarization are used to predict pi* resonance energies in associated nucleosides and nucleotides, for which static-exchange calculations were carried out. They observe slight shifts between the resonance energies in the isolated bases and those in the nucleosides.     

Analogs of purine nucleosides and purine mono-and polynucleotides

A number of 6-substituted 9-(1,5-dihydroxy-3-pentyl)purines were obtained from 5-amino-4,6-dichloropyrimidine. 5-Amino-4,6-dichloropyrimidine reacts with 2-hydroxymethylpyrrolidine to give 4-chloro-5-amino-6-(2-hydroxymethylpyrrolidino)pyrimidine.See [1] for communication IV.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 552–555, April, 1976.     

Mass spectrometry of nucleoside derivatives. Seleno analogs of purine and pyrimidine bases and nucleosides

Mass spectra of certain selenobases and selenonucleosides, and some of their trimethylsilyl and O,N-permethyl derivatives have been studied from the standpoint of structural characterization, and in order to ascertain the influence of selenium on normal fragmentation patterns. Molecular ion abundances of the selenouracils are intermediate between those of the corresponding oxygen and sulfur analogs. Fragmentation processes are similar to those of the corresponding normal bases and nucleosides but with additional ions resulting from expulsion of Se or SeH in most cases. Trimethylsilylation occurs at approximately the same rate as for normal bases and nucleosides but the products show decreasing stability with prolonged heating. A least squares procedure is demonstrated which generates monoisotopic mass patterns and assists in interpretation of the mass spectra.     

Analogs of purine nucleosides and purine mono- and polynucleotides

Selective protection of the amino and one of the hydroxyl groups of 6-substituted 9-(α,ω-dihydroxy-2-alkyl)purines was realized. A convenient method for the preparation of monophosphates was developed.     

Analogs of purine nucleosides and purine mono- and polynucleotides

On the basis of a comparison of the protolysis constants and vibrational frequencies it is shown that intermolecular interactions are present in 6-substituted 9-(,-dihydroxyalkyl)-purines and the corresponding mono- and diphosphates. In addition, in the case of the phosphates the existence of intramolecular interactions of electrostatic character between the phosphate group and the heteroring is also proposed. A comparison of the protolysis constants provides evidence for the different character of the interaction of the dihydroxyalkyl residue with the heteroring of the base in series of adenine and hypoxanthine derivatives.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1684–1689, December, 1974.     

Analogs of purine nucleosides and purine mono- and polynucleotides

Phosphorylation of 6-substituted 9-(1, 5-dihydroxy-3-pentyl)purines with 2-cyanoethyl phosphate in the presence of dicyclohexylcarbodiimide in anhydrous pyridine gave their 1, 5-diphosphates. Oligomers containing pyrophosphate and ester bonds were obtained by polycondensation of 1, 5-diphosphates of 6-dimethylamino- and 6-oxo-9-(1, 5-dihydroxy-3-pentyl)purines with the appropriate 9-(1, 5-dihydroxy-3-pentyl) purines.See [1] for communication V.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 693–696, May, 1976.     

Determination of purine nucleosides and their bases by high-performance liquid chromatography using co-immobilized enzyme reactors

A selective and sensitive assay of inosine, guanosine, hypoxanthine, guanine and xanthine by high-performance liquid chromatography with immobilized enzyme reactors was developed. The separation was achieved on a Capcell Pak C18 column (15 cm x 0.46 cm I.D.) with a mobile phase of 0.1 M phosphate buffer (pH 8.0) containing 7 mM sodium 1-hexanesulphonate and 0.1 mM p-hydroxyphenylacetic acid. The fluorimetric detection of hydrogen peroxide using immobilized peroxidase and p-hydroxyphenylacetic acid was applied to the assay of these compounds, which were oxidized to yield hydrogen peroxide in the presence of immobilized enzyme (purine nucleoside phosphorylase, guanase and xanthine oxidase). Enzyme reactions occurred sufficiently without post-column addition of reagents. Enzymes that catalysed the conversion of purine compounds were co-immobilized on aminopropyl controlled-pore glass packed in stainless-steel tubing. The detection limits were 30-200 pg per injection.     

Reactions of trimethylsilyl fluorosulfonyldifluoroacetate with purine and pyrimidine nucleosides

Difluorocarbene, generated from trimethylsilyl fluorosulfonyldifluoroacetate (TFDA), reacts with the uridine and adenosine substrates preferentially at the enolizable amide moiety of the uracil ring and the 6-amino group of the purine ring. 2′,3′-Di-O-benzoyl-3′-deoxy-3′-methyleneuridine reacts with TFDA to produce 4-O-difluoromethyl product derived from an insertion of difluorocarbene into the 4-hydroxyl group of the enolizable uracil ring. Reaction of the difluorocarbene with the adenosine substrates having the unprotected 6-amino group in the purine ring produced the 6-N-difluoromethyl derivative, while reaction with 6-N-benzoyl protected adenosine analogues gave the difluoromethyl ether product derived from the insertion of difluorocarbene into the enol form of the 6-benzamido group. Treatment of the 6-N-phthaloyl protected adenosine analogues with TFDA resulted in the unexpected one-pot conversion of the imidazole ring of the purine into the corresponding N-difluoromethylthiourea derivatives. Treatment of the suitably protected pyrimidine and purine nucleosides bearing an exomethylene group at carbons 2′, 3′ or 4′ of the sugar rings with TFDA afforded the corresponding spirodifluorocyclopropyl analogues but in low yields.     

The first synthesis and cytostatic activity of novel 6-(fluoromethyl)purine bases and nucleosides

Two alternative approaches to the synthesis of novel 6-(fluoromethyl)purine bases and nucleosides are described either by direct deoxyfluorination or by multistep functional group transformations starting from 6-(hydroxymethyl)purines. 6-(fluoromethyl)purine ribonucleoside displayed significant cytostatic effects.     

Simultaneous determination of purine bases, ribonucleosides and ribonucleotides by capillary electrophoresis-electrochemistry with a copper electrode

Simultaneous determination of purine bases, ribonucleosides and ribonucleotides was achieved by coupling capillary electrophoresis (CE) with wall-jet amperometric detection. A 200 μm diameter copper disk electrode was applied at working potential, +0.65 V vs. saturated calomel electrode. The current response of high sensitivity and stability was obtained in strong basic solutions which were suitable for satisfactory CE separations. The calibration curve was linear over 2–3 orders of magnitude and the limits of detection for adenine, guanine, xanthine, uric acid, adenosine, guanosine, adenosine-5′-monophosphate and guanosine-5′-monophosphate were below 9 fmol (S/N=3). The use of this method for the separation and detection of compounds present in human plasma samples was reported.     

Acyclic analogues of purine and imidazole nucleosides

Hydroxyl-protected derivatives of 1- and 3-(2-hydroxyethoxymethyl)imidazoles ( 4,5,7-10 ) have been prepared from 5-amino-4-carbamoylimidazoles ( 2 ). The protected derivatives were converted to acyclic analogues of imidazole nucleosides ( 6 ) or subjected to various cyclisation reactions leading to 9-(2-hydroxy-ethoxymethyl)-substituted 2-methyl-, 2-phenyl- and 2-azahypoxanthines ( 18,13 and 20 , respectively) and 1-methylguanine ( 28 ). For assignment of structures to isomeric imidazole and purine derivatives, ¹³C chemical shifts have been used.     

Chemical synthesis of cross-linked purine nucleosides

[reaction: see text] An efficient route to all of the possible cross-linked 2'-deoxypurines 1-3 has been developed by means of the Pd-mediated C-N bond formation in the key step. Utilizing this protocol, the synthesis of the first unnatural protected purine trimeric adduct 4 has been accomplished.     

Separation of purine bases, nucleosides and nucleotides by a column-switching technique combining reversed-phase and anion-exchange high-performance liquid chromatography

An on-line two-stage column chromatographic technique is described which combines reversed-phase and anion-exchange chromatography for the separation of purine nucleic acid components. The elution program applied, consisting of two gradient programmes, provides a separation of bases and nucleosides on the octadecyl silica column and a separation of the nucleotides on the anion-exchange column to which they have been switched at the beginning of the elution. This method is easy to modify for special problems and can be used when establishing a complete profile of purines.     

Simultaneous determination of myocardial nucleotides, nucleosides, purine bases and creatine phosphate by ion-pair high-performance liquid chromatography.

An ion-pair reversed-phase high-performance liquid chromatographic method is described for the separation and quantification of myocardial nucleotides, nucleosides, their metabolites and creatine phosphate-related compounds in a single run. Separation of a standard mixture containing 21 compounds was achieved on a 5-microns Hypersil ODS column with a 5-min isocratic elution (buffer: 0.1 M NaH2PO4, pH 5.5, containing 5.9 mM tetrabutylammonium hydrogen-sulphate) followed by a slow linear gradient to 17% acetonitrile. The method was applied to extracts of freeze-clamped rat heart tissue samples as well as to extracts of neonatal rat heart cardiomyocytes, and it provided good resolution of high-energy phosphates, including creatine phosphate, as well as of their degradation products.