Synthesis and structure of 2′-substituted 1-(1,3-dioxan-5-yl)uracils. Positive role of the Eu(fod)3 nmr shift reagent

The configuration of 1-(2-R-1,3-dioxan-5-yl)uracils and the conformation of the dioxane ring in these compounds were investigated by 1H NMR spectroscopy with the aid of the Eu(fod)3 shift reagent. It is shown that the dioxane ring exists in the preferred chair conformation with an axial orientation of the pyrimidine ring; this is confirmed by the resonance of the 5′-Ha proton in the form of a broad singlet with υ1/2υ8.5 Hz. An analysis of the spectral peculiarities of the synthesized compounds made it possible to establish the orientation of the substituents attached to the second C2 steric center. The three-dimensional structure of 1-(2, 2-dimethyl-1,3-dioxan-5-yl)uracil was determined by an x-ray diffraction study, and the axial orientation of the pyrimidine ring was confirmed. It is shown that significant flattening of the carbon part of the ring (ψ = 46.6 °) is observed in this molecule. An intramolecular (C6...O1, = 3.05 Å) hydrogen bond was observed in the molecule of this compound. © 1982 Plenum Publishing Corporation

Synthesis and structure of 2′-substituted 1-(1,3-dioxan-5-yl)uracils. Positive role of the Eu(fod)3 nmr shift reagent

The configuration of 1-(2-R-1,3-dioxan-5-yl)uracils and the conformation of the dioxane ring in these compounds were investigated by 1H NMR spectroscopy with the aid of the Eu(fod)3 shift reagent. It is shown that the dioxane ring exists in the preferred chair conformation with an axial orientation of the pyrimidine ring; this is confirmed by the resonance of the 5′-Ha proton in the form of a broad singlet with υ1/2υ8.5 Hz. An analysis of the spectral peculiarities of the synthesized compounds made it possible to establish the orientation of the substituents attached to the second C2 steric center. The three-dimensional structure of 1-(2, 2-dimethyl-1,3-dioxan-5-yl)uracil was determined by an x-ray diffraction study, and the axial orientation of the pyrimidine ring was confirmed. It is shown that significant flattening of the carbon part of the ring (ψ = 46.6 °) is observed in this molecule. An intramolecular (C6...O1, = 3.05 Å) hydrogen bond was observed in the molecule of this compound. © 1982 Plenum Publishing Corporation

Synthesis and structure of 2′-substituted 1-(1,3-dioxan-5-yl)uracils. Positive role of the Eu(fod)3 nmr shift reagent

The configuration of 1-(2-R-1,3-dioxan-5-yl)uracils and the conformation of the dioxane ring in these compounds were investigated by 1H NMR spectroscopy with the aid of the Eu(fod)3 shift reagent. It is shown that the dioxane ring exists in the preferred chair conformation with an axial orientation of the pyrimidine ring; this is confirmed by the resonance of the 5′-Ha proton in the form of a broad singlet with υ1/2υ8.5 Hz. An analysis of the spectral peculiarities of the synthesized compounds made it possible to establish the orientation of the substituents attached to the second C2 steric center. The three-dimensional structure of 1-(2, 2-dimethyl-1,3-dioxan-5-yl)uracil was determined by an x-ray diffraction study, and the axial orientation of the pyrimidine ring was confirmed. It is shown that significant flattening of the carbon part of the ring (ψ = 46.6 °) is observed in this molecule. An intramolecular (C6...O1, = 3.05 Å) hydrogen bond was observed in the molecule of this compound. © 1982 Plenum Publishing Corporation

Synthesis and structure of 2′-substituted 1-(1,3-dioxan-5-yl)uracils. Positive role of the Eu(fod)3 nmr shift reagent

The configuration of 1-(2-R-1,3-dioxan-5-yl)uracils and the conformation of the dioxane ring in these compounds were investigated by 1H NMR spectroscopy with the aid of the Eu(fod)3 shift reagent. It is shown that the dioxane ring exists in the preferred chair conformation with an axial orientation of the pyrimidine ring; this is confirmed by the resonance of the 5′-Ha proton in the form of a broad singlet with υ1/2υ8.5 Hz. An analysis of the spectral peculiarities of the synthesized compounds made it possible to establish the orientation of the substituents attached to the second C2 steric center. The three-dimensional structure of 1-(2, 2-dimethyl-1,3-dioxan-5-yl)uracil was determined by an x-ray diffraction study, and the axial orientation of the pyrimidine ring was confirmed. It is shown that significant flattening of the carbon part of the ring (ψ = 46.6 °) is observed in this molecule. An intramolecular (C6...O1, = 3.05 Å) hydrogen bond was observed in the molecule of this compound. © 1982 Plenum Publishing Corporation

Purification and Characterization of West Nile Virus Nucleoside Triphosphatase (NTPase)/Helicase: Evidence for Dissociation of the NTPase and Helicase Activities of the Enzyme

The nucleoside triphosphatase (NTPase)/helicase associated with nonstructural protein 3 of West Nile (WN) virus was purified from cell culture medium harvested from virus-infected Vero cells. The purification procedure included sequential chromatography on Superdex-200 and Reactive Red 120 columns, followed by a concentration step on an Ultrogel hydroxyapatite column. The nature of the purified protein was confirmed by immunoblot analysis using a WN virus-positive antiserum, determination of its NH(2) terminus by microsequencing, and a binding assay with 5′-[(14)C]fluorosulfonylbenzoyladenosine. Under optimized reaction conditions the enzyme catalyzed the hydrolysis of ATP and the unwinding of the DNA duplex with k(cat) values of 133 and 5.5 × 10(−3) s(−1), respectively. Characterization of the NTPase activity of the WN virus enzyme revealed that optimum conditions with respect to the Mg(2+) requirement and the monovalent salt or polynucleotide response differed from those of other flavivirus NTPases. Initial kinetic studies demonstrated that the inhibition (or activation) of ATPase activity by ribavirin-5′-triphosphate is not directly related to changes in the helicase activity of the enzyme. Further analysis using guanine and O(6)-benzoylguanine derivatives revealed that the ATPase activity of WN virus NTPase/helicase may be modulated, i.e., increased or reduced, with no effect on the helicase activity of the enzyme. On the other hand the helicase activity could be modulated without changing the ATPase activity. Our observations show that the number of ATP hydrolysis events per unwinding cycle is not a constant value