Synthesis of AZT analogues: 7-(3-azido-2-hydroxypropyl)-, 7-(3-amino-2-hydroxypropyl)-,7-(3-triazolyl-2-hydroxypropyl)theophylline

Nucleophilic displacement of the tosyloxy group in 7-(2-hydroxy-3-p-toluenesulfonyloxypropyl)theophylline (1) with azide anion afforded 7-(3-azido-2-hydroxypropyl)theophylline (2). Reduction of the 3-azido group in 2 with Ph3P/Py/NH4OH afforded the 3-amino derivative 4, alternatively obtained by regioselective amination of 7-(2,3-epoxypropyl)theophylline (3). Selective acetylation of 4 gave the N-acetyl derivative 5. 1,3-Dipolar cycloaddition of the azide group in 2 with N1-propargyl thymine (6) afforded the regioisomeric triazole 7.

Electrospray tandem mass-spectrometric analysis of diastereo- and stereoisomeric pyrimidine nucleoside analogues based on the 1,3-dihydrobenzo[c]furan core

Electrospray mass spectrometry and tandem mass spectrometry have aided the structural characterization of the diastereoisomeric cis- and trans-1-(3-benzoyloxymethyl-1,3-dihydrobenzo[c]furan-1-yl)thymines and the four enantiomerically pure stereoisomers of uracil analogues. Low-energy collision-induced dissociation MS/MS analysis of the various precursor molecular and cluster ions confirmed the characteristic fingerprint pattern obtained in the conventional electrospray spectra and allowed a convenient method for the characterization of novel 1,3-dihydrobenzo[c]furan nucleosides.

Determination of the anomeric configuration of glycosyl esters of nucleoside pyrophosphates and polyisoprenyl phosphates by fast-atom bombardment tandem mass spectrometry

Collision-induced dissociation of the deprotonated molecules of glycosyl esters of nucleoside pyrophosphates and polyisoprenyl (dolichyl and polyprenyl) phosphates results in distinct fragmentation patterns that depend on cis-trans configuration of the phosphodiester and 2″ (or 2', respectively)-hydroxyl groups of the glycosyl residue. At the collision-offset voltage of 0. 5 V, sugar nucleotides with cis configuration produce only one very abundant fragment of nucleoside monophosphate, whereas compounds with trans configuration give weak signals for nucleoside di- and mono-phosphates and their dehydration products. These fragmentation patterns are largely preserved at higher collision energy, with the exception that, for sugar nucleotides with trans configuration, the characteristic signals are much more abundant and a novel diagnostic fragment of [ribosyl(deoxyribosyl)-5'-P2O5 - H](-) is generated. In the case of polyisoprenyl-P-sugars, polyisoprenyl phosphate ion is the only fragment observed for compounds with trans configuration, whereas in compounds with cis configuration, this ion is accompanied by another abundant fragment, which is derived from the cleavage across the sugar ring and corresponds to [polyisoprenyl-PO4-(C2H3O)](-). The relative intensity ratio of the latter ion to the [polyisoprenyl-HPO4](-) ion is close to 1 for compounds with cis configuration, but it is only about 0. 01 for compounds with trans configuration. This ratio may serve, therefore, as a diagnostic value for determination of the anomeric configuration of glycosyl esters of polyisoprenyl phosphates. It is proposed that the observed differences in fragmentation patterns of cis-trans sugar nucleotides and polyisoprenyl-P-sugars could be explained in terms of kinetic stereoelectronic effect, and a speculative mechanism of fragmentation of compounds with trans configuration is presented. For compounds with cis configuration, formation of a hydrogen bond between the C-2″(2') hydroxyl and the phosphate group could play a crucial role in directing the specific fragmentation reactions. Consequently, the described empirical rules would hold only for compounds that have a free 2″(2')-hydroxyl group and no alternative charge location. Owing to its simplicity, sensitivity, and tolerance of impurities, fast-atom bombardment-tandem mass spectrometry represents a suitable method for determination of the anomeric linkage of glycosyl esters of nucleoside pyrophosphates and polyisoprenyl phosphates if the absolute configuration of glycosyl residue is known and the compound fulfills the above-mentioned requirements.

Determination of the anomeric configuration of glycosyl esters of nucleoside pyrophosphates by fast-atom bombardment tandem mass spectrometry

Very low energy collision-induced dissociation of the deprotonated molecules of glycosyl esters of nucleoside pyrophosphates results in distinct fragmentation patterns that depend on the cis-trans configuration of the phosphodiester and 2″-hydroxyl groups of the glycosyl residue. In tandem mass spectrometry, sugar nucleotides with cis configuration produce only one, very abundant fragment that corresponds to nucleoside monophosphate, whereas nucleotides with trans configuration give weak signals for the nucleoside di- and monophosphates and their dehydration products. This empirical rule holds for sugar nucleotides that have a free 2″-hydroxyl group and no alternative charge location. Owing to its simplicity, sensitivity, and tolerance of impurities, fast-atom bombardment-tandem mass spectrometry represents a suitable method for determination of the anomeric linkage of glycosyl esters of nucleoside pyrophosphates if the absolute configuration of glycosyl residue is known and the compound fulfills the above-mentioned requirements.