Synthesis of phosphonated carbocyclic 2'-oxa-3'-aza-nucleosides: novel inhibitors of reverse transcriptase.
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Citations
1,3-Dipolar cycloadditions: applications to the synthesis of antiviral agents.
Organocatalytic asymmetric formal [3 + 2] cycloaddition with in situ-generated N-carbamoyl nitrones.
Microwave‐Assisted 1,3‐Dipolar Cycloaddition: an Eco‐Friendly Approach to Five‐Membered Heterocycles
Antiviral activity of seed extract from Citrus bergamia towards human retroviruses
Synthesis of C-4′Truncated Phosphonated Carbocyclic 2′-Oxa-3′-azanucleosides as Antiviral Agents
References
Development and use of quantum mechanical molecular models. 76. AM1: a new general purpose quantum mechanical molecular model
Antiviral drugs in current clinical use.
Nucleoside syntheses, XXII1) Nucleoside synthesis with trimethylsilyl triflate and perchlorate as catalysts
Molecular targets for AIDS therapy
Structural characterization of a partly folded apomyoglobin intermediate.
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Frequently Asked Questions (21)
Q2. What is the role of ddNs in antiviral therapy?
The biological activity of nucleoside analogues (ddNs) showing antiviral properties is strictly linked to their conversion, through cellular enzymes, to the corresponding 5′-mono-, di, and triphosphates, which interact with viral reverse transcriptase (RT) or interfere with cell growth, slowing the cell cycle progression.
Q3. What is the role of phosphate analogues in the synthesis of antivir?
Those enzimatically and chemically stable phosphonate analogues, which mimic the nucleoside monophosphates, are able to overcome the instability of nucleotides toward phosphodiesterases and to enhance their cellular uptake by bypassing the initial enzymatic phosphorylation and could potentially be effective antiviral agents.
Q4. What is the way to deliver a nucleoside?
A good delivery system for a nucleoside across membranes might be represented by phosphotriester molecules, which should ensure the absorption and the transport of the active molecule and should then be able to deliver intracellular monophosphate forms.
Q5. What is the role of phosphonates in RT?
More importantly, the obtained phosphonate nucleosides seem to act as RT inhibitors, when tested in a simple cell-free assay, as powerfully as AZT is, opening new perspectives in future investigations on their possible use as therapeutic agents, particularly in antiretroviral and anti-HBV chemotherapy.
Q6. What is the way to test a phosphonate nucleoside?
Phosphonated N,O-nucleosides, containing thymine,fluorouracil, and cytosine, have been synthesized in good yields by 1,3-dipolar cycloaddition methodology.
Q7. What is the cytotoxicity of phosphocyclic 2′-oxa3′?
Phosphonated carbocyclic 2′-oxa3′-aza-nucleosides, while showing low levels of cytotoxicity, exert a specific inhibitor activity on two different reverse transcriptases, which is comparable with that of AZT, opening new perspectives on their possible use as therapeutic agents, in anti-retroviral and anti-HBV chemotherapy.
Q8. What are the main reasons for the increase in the number of modified nucleosides?
In particular, modified nucleosides have been proved to efficiently inhibit in vitro and in vivo virus infections caused by HIV, HBV, and HTLV-1.1
Q9. What is the role of the new compounds in apoptosis?
considering the pivotal role of apoptosis as a mechanism, triggered by cellular signals as well as by a variety of drugs, for the controlled removal of dead cells, particularly of the immune system, the authors assayed the ability of the new compounds to specifically induce apoptosis in the same cell lines.
Q10. How many times did the cells have to be exposed to the PBMC crude extract?
Cells were exposed under optimal culture conditions to concentrations of AdT-phosphonate (AdT-P, 11a), AdC-phosphonate (AdC-P, 11b) and AdF-phosphonate (AdF-P, 11c), ranging from 16 to 1000 µM, or control medium for the times indicated.
Q11. What is the effect of irradiation on the methylene protons?
In particular, for â-compounds 11, irradiation of H1′ increased the resonance of H6, H4′, and H6′b (the downfield resonance of methylene protons at C6′).
Q12. What is the cytotoxicity of the phosphonate nucleosides?
The results indicate that the synthesized phosphonate nucleosides presented low levels of cytotoxicity assessed by a conventional assay to detect viability, such as the trypan blue exclusion test, as well as by detection of cell death by apoptosis.
Q13. What is the effect of phosphonates on RT?
following exposure of the nucleosides to the crude extract from (PBMCs), all phosphonates completely inhibited the formation of amplified products at10 nM concentration, with the exception of ADF, which was completely inactive.
Q14. What is the effect of irradiation on the H5 resonance?
in compound 6 irradiation of the H5 resonance induces a positive NOE effect on H3 proton and on the downfield resonance of methylene protons at C4, indicating a cis relationship between these protons.
Q15. How long did the assay take to detect apoptosis?
Before being assayed, the new compounds and AZT were incubated with a crude extract from human peripheral blood mononuclear cells (PBMCs) stimulated with PHA for 72 h.
Q16. What is the effect of isoxazolidines on the anomeric center?
These results show that the coupling reaction of isoxazolidines with silylated bases occurs without selectivity with respect to the anomeric center.
Q17. What is the stereochemical outcome of the cycloaddition process?
The stereochemical outcome of the cycloaddition process can be explained by considering that nitrone 5 exists as a mixture of E/Z isomers: NOE data indicatedthat the Z form is predominant (Z/E ratio ) 5:1).
Q18. What is the cis isomer of nitrone 5?
the major product 6 could be formed by the (Z)-nitrone reacting in an exo mode or by the (E)-nitrone reacting in an endo mode, in agreement with the results reported for similar R-alkoxynitrones.10 AM1 calculations11 give theoretical support to the experimental data, indicating that the (E)-isomer as the more reactive form of nitrone 5: the (E)-endo transition state leading to 6 is about 0.45 kcal/mol more stable than the (E)-exo one leading to trans stereoisomer 7.
Q19. What are the main problems associated with the aza-nucleosides?
several problems associated with this kind of nucleoside analogues, due to their high toxicity and the appearance of cross-resistance, have led to the search for different structural solutions which have afforded new prodrugs comparable in their antiviral activity to the clinically used nucleoside analogues, but without their drawbacks.
Q20. What is the effect of irradiation on the aqueous nitrogen?
when H6′b was irradiated, enhancements of the H1′, H4′, and H6′a signals were observed, while irradiation of H6′a gives rise to a positive NOE effect for H6 and H6′b.
Q21. how many isomeric isoxazolidines are used in compound 7?
The cycloaddition with vinyl acetate leads to a mixture of epimeric isoxazolidines 6 and 7 (90% overall yield) in a relative ratio 2.6:1.