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11.
The convenient method for the preparation of N4-substituted cytosines is described. The irradiation with UV light of N-(1H-2-oxo-4-pyrimidinyl) amino acids provides the proper N4-substituted cytosines in a good yield. 相似文献
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13.
The mass spectral fragmentation of the six 2′-, 3′- and 4′ -hydroxy substituted 4- and 2-azastilbenes is discussed and fragmentation pathways, elucidation of which were assisted by accurate mass measurements and metastable transitions, are proposed. It has been found that the position of the hydroxystyryl group in the pyridine ring may be deduced on the basis of mass spectral fragmentation patterns. 相似文献
14.
The mass fragmentation of twelve new 2- and 4-alkylthio substituted derivatives of uracils is discussed and fragmentation pathways, elucidation of which was assisted by accurate mass measurements and metastable transitions, are proposed. It has been found that the position of uracil ring thiation may be deduced on the basis of mass spectral fragmentation patterns. 相似文献
15.
Bozenna Golankiewicz Tomasz Ostrowski Peter Leonard Frank Seela 《Helvetica chimica acta》2002,85(1):388-398
The protected 2′‐deoxyguanosine derivatives 5a – c undergo N9→N7 isomerization in the melt and in solution. The rate of isomerization is much faster than in the case of the corresponding ribonucleosides and occurs even in the absence of a catalyst. In the melt (195°, 2 min), the N2,3′‐O,5′‐O‐tris(4‐toluoyl) derivative 5b and the N2‐acetyl‐3′,5′‐bis‐O‐[(tert‐butyl)dimethylsilyl] derivative 5c gave anomeric mixtures of the N7‐isomers 9b / 10b (43%) and 9c / 10c (55%), respectively. In addition, the N9‐α‐D ‐anomers 8b and 8c were obtained. Different from 5b , the isomerization of peracetylated 5a resulted in low yields. Compound 5b was also prone to isomerization performed in solution (toluene, 100°, 5 min; chlorobenzene, 120°, 5 min), furnishing the N7‐regioisomers in 24–53% yield. The highest yield of the N9→N7 isomerization occurred in the presence of 2‐deoxy‐3,5‐di‐O‐(4‐toluoyl)‐α‐D ‐erythro‐pentofuranosyl chloride. 相似文献
16.
Alicja Zasada-Parzyska Krzysztof Golankiewicz 《Journal of mass spectrometry : JMS》1982,17(12):614-616
The mass fragmentation of three dinucleotide analogues in which D -ribose phosphodiester linkages were replaced by a three methylene unit chain has been investigated. The fragmentation pathways were proposed on the basis of high resolution data and metastable transitions. These compounds demonstrated a unique fragmentation with the formation of the fragment ion containing nitrogen at the end of the C3H6 chain. 相似文献
17.
The mass fragmentation of bromohydrins of uracil derivatives is discussed. Fragmentation pathways have been proposed on the basis of high-resolution data and metastable transitions. The distinct influence of substituents in position 5 of uracil on the fragmentation pathway has been observed. 相似文献
18.
The aim of the experiment was to investigate the effect of vitrification on viability and the cell cycle of bovine cumulus cells and fibroblasts after culture with or without serum starvation. In all vitrified-thawed bovine somatic cells, the number of samples that reached the confluence stage was high (50 to 100%). The viability of vitrified somatic cells depended on the concentration of the cells. The viability was higher for cells vitrified at the concentration of 10 x 10(6) per ml than for cells vitrified at a concentration of 1 x 10(6) per ml (p < 0.05; for cumulus cell, and fibroblast). Time of cell starving has had no impact on their susceptibility to vitrification in case of vitrified cumulus cells. Starving time caused shifts in proportions of subsequent cell cycle phases of vitrified fibroblasts and cumulus cells. In conclusion, the bovine cumulus and fibroblast cells can be cryopreserved successfully by vitrification procedure. 相似文献
19.
J J Langer H Wójtowicz K Golankiewicz 《Journal of photochemistry and photobiology. B, Biology》1989,4(1):15-20
5-Fluorouracil residues can form cyclobutane-type photodimers in a direct excitation stacking-controlled process. The stacking also has an important effect on the photohydration of uracil and 5-fluorouracil in our model compounds 5RUra(CH2)35FUra, where R = H, CH3, C2H5, C3H7, F or Cl. 相似文献
20.
Adam S. Plaziak Lech Celewicz Jaroslaw Spychala Krzysztof Golankiewicz 《Journal of mass spectrometry : JMS》1990,25(2):93-96
The electron-impact-induced mass fragmentations of methyl esters of N-(1H-2-oxo-4-pyrimidinyl)ainino acids are reported. The loss of a ·COOCH3 radical and the elimination of a methanol molecule were observed and possible mechanisms of these processes are proposed. The loss of a ·COOH radical and elimination of water were established, which suggests the rearrangement of the investigated esters into isomeric N-4-pyrimidinylamino acids. 相似文献