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Gennaro Piccialli - One of the best experts on this subject based on the ideXlab platform.
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synthesis of c6 pyridylpurine nucleosides by reaction of Nebularine n1 oxide with pyridinyl grignard reagents
European Journal of Organic Chemistry, 2015Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Fabrizia Nici, Vincenzo Piccialli, Brunella Pinto, Daniele Dalonzo, Luciano Mayol, Gennaro PiccialliAbstract:A general synthesis of C6-pyridylpurine nucleosides is described. The reported synthetic procedure exploits the regioselective addition of pyridinyl Grignard reagents, obtained by bromine/magnesium exchange between mono- or dihalopyridines and iPrMgCl, to the C6–N1–O– moiety of Nebularine N1-oxide. The regioselective transmetallation of unsymmetrical dihalopyridines with iPrMgCl allowed C6-halopyridylpurine nucleosides to be obtained through the addition of halopyridinyl Grignard reagents. The presence of a halogenated pyridine ring in these nucleosides allows for further useful synthetic transformations.
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synthesis of 2 6 dialkyl aryl purine nucleosides by exploiting the reactivity of Nebularine n1 oxide towards grignard reagents
European Journal of Organic Chemistry, 2013Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Vincenzo Piccialli, Luciano Mayol, Valentina Datri, Gennaro PiccialliAbstract:The synthesis of 2,6-dialkyl(aryl)purine nucleosides by application of a double addition of Grignard reagents to N1-oxide purine nucleosides is described. The synthetic protocol exploits the reactivity of both the C6–N1–O– and C2–N1–O– moieties of the purine base. The overall process consists of initial Grignard reagent addition to the C6 of Nebularine N1-oxide followed by aromatization to give a C6-substituted nucleoside. Regeneration of the N1-oxide is then followed by a second Grignard addition at C2 causing the opening of the pyrimidine ring. Cyclization of the transiently opened pyrimidine is then driven by aromatization of the system to afford the final purine system.
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probing the reactivity of Nebularine n1 oxide a novel approach to c 6 c substituted purine nucleosides
Tetrahedron, 2011Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Vincenzo Piccialli, Jussara Amato, Valentina Datri, Gennaro PiccialliAbstract:Abstract A novel approach to the synthesis of purine nucleoside analogues, featuring the reaction of the C6– N 1–O − aldonitrone moiety of 9-ribosyl-purine (Nebularine) N 1-oxide with some representative dipolarophiles, as well as Grignard reagents, is reported. Addition of Grignard reagents to the electrophilic C-6 carbon of the substrate allows a facile access to C-6 C -substituted purine nucleosides without using metal catalysts. 1,3-Dipolar cycloaddition processes lead to novel nucleoside analogues via opening, degradation or ring-enlargement of the pyrimidine ring of the base system of the first-formed isoxazoline or isoxazolidine cycloadduct.
Stefano Derrico - One of the best experts on this subject based on the ideXlab platform.
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5 chloro 5 deoxy 2 3 o isopropylidene 6 fluoro Nebularine
Molbank, 2019Co-Authors: Andrea Patrizia Falanga, Maria Marzano, Monica Terracciano, Stefano DerricoAbstract:In this paper, we report on the synthesis and spectroscopic characterization of the novel nucleoside 5′-chloro-5′-deoxy-2′,3′-O-isopropylidene-6-fluoro Nebularine, obtained as a side product during the second step of the synthesis of 5′-fluoro-5′-deoxy-5-aminoimidazole-4-carboxamide-β-d-riboside (5′-F-AICAR), a non-phosphorylable analogue of 5-aminoimidazole-4-carboxamide-β-d-riboside (AICAR).
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synthesis of c6 pyridylpurine nucleosides by reaction of Nebularine n1 oxide with pyridinyl grignard reagents
European Journal of Organic Chemistry, 2015Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Fabrizia Nici, Vincenzo Piccialli, Brunella Pinto, Daniele Dalonzo, Luciano Mayol, Gennaro PiccialliAbstract:A general synthesis of C6-pyridylpurine nucleosides is described. The reported synthetic procedure exploits the regioselective addition of pyridinyl Grignard reagents, obtained by bromine/magnesium exchange between mono- or dihalopyridines and iPrMgCl, to the C6–N1–O– moiety of Nebularine N1-oxide. The regioselective transmetallation of unsymmetrical dihalopyridines with iPrMgCl allowed C6-halopyridylpurine nucleosides to be obtained through the addition of halopyridinyl Grignard reagents. The presence of a halogenated pyridine ring in these nucleosides allows for further useful synthetic transformations.
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synthesis of 2 6 dialkyl aryl purine nucleosides by exploiting the reactivity of Nebularine n1 oxide towards grignard reagents
European Journal of Organic Chemistry, 2013Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Vincenzo Piccialli, Luciano Mayol, Valentina Datri, Gennaro PiccialliAbstract:The synthesis of 2,6-dialkyl(aryl)purine nucleosides by application of a double addition of Grignard reagents to N1-oxide purine nucleosides is described. The synthetic protocol exploits the reactivity of both the C6–N1–O– and C2–N1–O– moieties of the purine base. The overall process consists of initial Grignard reagent addition to the C6 of Nebularine N1-oxide followed by aromatization to give a C6-substituted nucleoside. Regeneration of the N1-oxide is then followed by a second Grignard addition at C2 causing the opening of the pyrimidine ring. Cyclization of the transiently opened pyrimidine is then driven by aromatization of the system to afford the final purine system.
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probing the reactivity of Nebularine n1 oxide a novel approach to c 6 c substituted purine nucleosides
Tetrahedron, 2011Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Vincenzo Piccialli, Jussara Amato, Valentina Datri, Gennaro PiccialliAbstract:Abstract A novel approach to the synthesis of purine nucleoside analogues, featuring the reaction of the C6– N 1–O − aldonitrone moiety of 9-ribosyl-purine (Nebularine) N 1-oxide with some representative dipolarophiles, as well as Grignard reagents, is reported. Addition of Grignard reagents to the electrophilic C-6 carbon of the substrate allows a facile access to C-6 C -substituted purine nucleosides without using metal catalysts. 1,3-Dipolar cycloaddition processes lead to novel nucleoside analogues via opening, degradation or ring-enlargement of the pyrimidine ring of the base system of the first-formed isoxazoline or isoxazolidine cycloadduct.
Muhsin Konuk - One of the best experts on this subject based on the ideXlab platform.
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biosynthesis of Nebularine purine 9 β d ribofuranoside involves enzymic release of hydroxylamine from adenosine
Phytochemistry, 1995Co-Authors: Eric G Brown, Muhsin KonukAbstract:Abstract Biosynthesis of the antibiotic Nebularine (purine-9-β- d -ribofuranoside) by Lepista nebularis and Streptomyces yokosukanensis has been studied and a novel enzymic activity is described which deaminates adenosine to release hydroxylamine. Use of 14 C-labelled nucleosides showed that adenosine was the more immediate precursor of Nebularine. That formation of Nebularine involves direct incorporation of adenosine and does not involve prior catabolism and re-use of catabolic fragments, was shown by locating 82% of the incorporated radioactivity from [8- 14 C]adenosine in C-8 of Nebularine. A crude Nebularine-forming enzymic extract was fractionated by (NH 4 ) 2 SO 4 precipitation and the activity recovered in the 100% satn supernatant; it was not sedimented by centrifuging for 90 min at 113 000 g. Further purification was achieved by chromatography of Sephacryl S-200 (173-fold) and on BrCN-activated Sepharose 4B (320-fold). Lability of the enzyme during concentration, by various techniques, obviated sequential use of these steps. Activity was not stimulated by pyridine nucleotides or flavins, and a range of metal ions were without effect. Various purine riboside analogues were not inhibitory, although some end-product inhibition was seen with Nebularine. Gel-filtration and SDS-PAGE indicated a M r of 9500–10000 for the enzyme. That hydroxylamine is a product of the catalysed reaction was demonstrated chemically and by MS. Use of [ 15 N-amino]adenosine confirmed that the hydroxylamine originates from the 6-amino group of adenosine. The quantitative relationship between Nebularine production and metabolism of adenosine to other compounds was studied. Of the total radioactivity from [8- 14 C]adenosine recovered, 3% was in Nebularine. The work describes the first reported natural occurrence, in a free state, of purine and its 5′-ribotide.
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plant cytotoxicity of Nebularine purine riboside
Phytochemistry, 1994Co-Authors: Eric G Brown, Muhsin KonukAbstract:Abstract The plant cytotoxicity of Nebularine, a purine riboside antibiotic produced by the fungus Lepista ( Clitocybe ) nebularis , has been examined.
Zafri M Humayun - One of the best experts on this subject based on the ideXlab platform.
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Nebularine 9 2 deoxy β d ribofuranosylpurine has the template characteristics of adenine in vivo and in vitro
Mutation Research, 1997Co-Authors: Sayeedur M Rahman, Zafri M HumayunAbstract:Abstract Nebularine (9-β- d -ribofuranosylpurine; Nb) is a naturally occurring nucleoside with structural features suggestive of a universal base. However, previous observations based on thermal melting characteristics of oligonucleotides suggested that Nb formed stable pairs only with thymine. To determine the template characteristics of Nb, we constructed M13 viral single-stranded DNA (ssDNA) molecules bearing a single site-specific deoxyNebularine (9-2′-deoxy-β- d -ribofuranosylpurine) residue. The ssDNA constructs were transfected into Escherichia coli cells to determine the specificity of base insertion opposite Nb, as well as to determine the effect of Nb on the replicability of the transfected DNA. Base insertion opposite Nb, analyzed by a multiplex sequencing technology, suggests that Nb has the template characteristics of adenine. Analysis of DNA replicability, measured as transfection efficiency, indicates that Nb does not block DNA replication. UV irradiation of host cells before transfection did not significantly affect survival or base insertion specificity within the limits of multiplex sequencing technology employed, suggesting that inducible mutagenic phenomena appear to have only minor effects on translesion synthesis across Nb. In addition, in vitro DNA elongation experiments on oligonucleotide templates using E. coli DNA polymerase I (Klenow fragment) as the model polymerase showed that Nb templates for T, but not for other bases under the tested conditions. The data reported in this communication underscore the importance of base-pair geometry as a specificity-determinant during base insertion by replicative polymerases.
Giorgia Oliviero - One of the best experts on this subject based on the ideXlab platform.
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synthesis of c6 pyridylpurine nucleosides by reaction of Nebularine n1 oxide with pyridinyl grignard reagents
European Journal of Organic Chemistry, 2015Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Fabrizia Nici, Vincenzo Piccialli, Brunella Pinto, Daniele Dalonzo, Luciano Mayol, Gennaro PiccialliAbstract:A general synthesis of C6-pyridylpurine nucleosides is described. The reported synthetic procedure exploits the regioselective addition of pyridinyl Grignard reagents, obtained by bromine/magnesium exchange between mono- or dihalopyridines and iPrMgCl, to the C6–N1–O– moiety of Nebularine N1-oxide. The regioselective transmetallation of unsymmetrical dihalopyridines with iPrMgCl allowed C6-halopyridylpurine nucleosides to be obtained through the addition of halopyridinyl Grignard reagents. The presence of a halogenated pyridine ring in these nucleosides allows for further useful synthetic transformations.
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synthesis of 2 6 dialkyl aryl purine nucleosides by exploiting the reactivity of Nebularine n1 oxide towards grignard reagents
European Journal of Organic Chemistry, 2013Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Vincenzo Piccialli, Luciano Mayol, Valentina Datri, Gennaro PiccialliAbstract:The synthesis of 2,6-dialkyl(aryl)purine nucleosides by application of a double addition of Grignard reagents to N1-oxide purine nucleosides is described. The synthetic protocol exploits the reactivity of both the C6–N1–O– and C2–N1–O– moieties of the purine base. The overall process consists of initial Grignard reagent addition to the C6 of Nebularine N1-oxide followed by aromatization to give a C6-substituted nucleoside. Regeneration of the N1-oxide is then followed by a second Grignard addition at C2 causing the opening of the pyrimidine ring. Cyclization of the transiently opened pyrimidine is then driven by aromatization of the system to afford the final purine system.
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probing the reactivity of Nebularine n1 oxide a novel approach to c 6 c substituted purine nucleosides
Tetrahedron, 2011Co-Authors: Stefano Derrico, Giorgia Oliviero, Nicola Borbone, Vincenzo Piccialli, Jussara Amato, Valentina Datri, Gennaro PiccialliAbstract:Abstract A novel approach to the synthesis of purine nucleoside analogues, featuring the reaction of the C6– N 1–O − aldonitrone moiety of 9-ribosyl-purine (Nebularine) N 1-oxide with some representative dipolarophiles, as well as Grignard reagents, is reported. Addition of Grignard reagents to the electrophilic C-6 carbon of the substrate allows a facile access to C-6 C -substituted purine nucleosides without using metal catalysts. 1,3-Dipolar cycloaddition processes lead to novel nucleoside analogues via opening, degradation or ring-enlargement of the pyrimidine ring of the base system of the first-formed isoxazoline or isoxazolidine cycloadduct.
