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101.
Starting from a readily available enantiopure building block, a straightforward enantioselective approach to 3′-methyl-2′,3′-β-oxirane-fused carbanucleosides bearing adenosine analogues is detailed. The key steps in the syntheses involved a lipase-catalyzed regioselective monoacylation of a diol to obtain the key intermediate and direct coupling of this key intermediate with diversely substituted purine nucleobases under Mitsunobu reaction conditions providing only the N9 target molecules. 相似文献
102.
H. M. Liebich G. Xu C. Di Stefano R. Lehmann H. U. Häring P. Lu Y. Zhang 《Chromatographia》1997,45(1):396-401
Summary Modified nucleosides excreted in urine have been studied as potential diagnostic markers for cancer and AIDS, and as indicators
for the whole-body turnover of RNA. Until now, reversed-phase (RP) HPLC and, to some extent, immunoassays are the preferred
analytical methods for urinary nucleosides. A new capillary electrophoretic method for the analysis of normal and modified
nucleosides in urine has been developed and optimized in our laboratory. The separation of nucleosides extracted from normal
human urine on phenyl boronic acid affinity chromatography columns was performed in uncoated 565 mm (500 mm to detection window)
× 50 μm i.d. capillary tubing using a 300 mM SDS—25 mM borate—50 mM phosphate buffer (pH 6.7), a 45-s load, a voltage of 7.5
kV (41 μA) and UV detection at 260 and 210 nm. The average recovery of the nucleosides was 91 %. The calibration curves were
linear over all physiological and pathophysiological concentration ranges and the limits of detection were at micromolar levels.
Reproducibility of migration times were better than 1 % (coefficient of variation,CV), and the reproducibilities of the determined concentrations were better than 5 % for standards and 6–15 % for extracted
urine. The developed method was used to quantify 15 normal and modified nucleosides in 25 normal urines to establish reference
ranges. The analysis time was less than 45 min.
Dedicated to Professor E. Bayer on the occasion of his 70th birthday.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996. 相似文献
103.
Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2020,58(1):15-30
This is the third and the last part of three closely interrelated reviews dealing with computation of 1H nuclear magnetic resonance chemical shifts and 1H–1H spin–spin coupling constants. Present review deals with the computation of these parameters in biologically active natural products, carbohydrates, and other molecules of biological origin focusing on stereochemical applications of computational 1H nuclear magnetic resonance to these objects. 相似文献
104.
105.
106.
Dr. Christoph Kreutz Prof. Dr. Ronald Micura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11634-11643
Although numerous reports on the synthesis of atom‐specific 15N‐labeled nucleosides exist, fast and facile access to the corresponding phosphoramidites for RNA solid‐phase synthesis is still lacking. This situation represents a severe bottleneck for NMR spectroscopic investigations on functional RNAs. Here, we present optimized procedures to speed up the synthesis of 15N(1) adenosine and 15N(1) guanosine amidites, which are the much needed counterparts of the more straightforward‐to‐achieve 15N(3) uridine and 15N(3) cytidine amidites in order to tap full potential of 1H/15N/15N‐COSY experiments for directly monitoring individual Watson–Crick base pairs in RNA. Demonstrated for two preQ1 riboswitch systems, we exemplify a versatile concept for individual base‐pair labeling in the analysis of conformationally flexible RNAs when competing structures and conformational dynamics are encountered. 相似文献
107.
Yu Tang Rebecca L. Grange Oliver D. Engl Scott J. Miller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(52):e202201661
Acylated nucleoside analogues play an important role in medicinal chemistry and are extremely useful precursors to various other nucleoside analogues. However, chemoselective acylation of nucleosides usually requires several protection and deprotection steps due to the competing nucleophilicity of hydroxy and amino groups. In contrast, direct protecting-group-free chemoselective acylation of nucleosides is a preferred strategy due to lower cost and fewer overall synthetic steps. Herein, a simple and efficient chemoselective acylation of nucleosides and nucleotides under mild reaction conditions, giving either O- or N-acylated products respectively with excellent chemoselectivity is reported. 相似文献
108.
S?awomir Boncel 《Tetrahedron》2010,66(43):8450-8457
By controlling the temperature or reaction time in the base-catalysed Michael-type addition of 5-substituted uracil derivatives we were able to synthesise N-1 or N-3 uracil adducts using methyl acrylate and acrylonitrile as acceptors. The mechanism of this chemical inequivalence was established using 1H NMR spectroscopic studies. The investigations revealed that formation of the N-1 adduct was achievable under kinetically controlled conditions irrespective to the type of the base used (TEA, DBU). In turn, synthesis of the N-3 adducts proceeded from the initially formed N-1,N-3 diadduct via a retro-Michael reaction which dominates at elevated temperature or prolonged reaction time. 相似文献
109.
A straightforward procedure for the preparation of nucleoside analogue 1 and its regioisomer 2 containing a dihydro-1,4-dithiin as sugar moiety has been accomplished in four steps by our readily available heterocyclic system 5. Nucleobase insertion was carried out by direct addition of N4-acetylcytosine to sulfoxide derivatives via Pummerer-type glycosidation reaction. 相似文献
110.