7-deazaadenine and 3-deazaadenine

On the basis of the potent inhibitory activity of neplanocin A (1) against S-adenosylhomocysteine (AdoHcy) hydrolase, we analyzed the comprehensive structure-activity relationships by modifying the adenine and carbasugar moiety of 1 to find the pharmacophore in the active site of the enzyme. The introduction of 7-deazaadenine instead of adenine eliminated the inhibitory activity against the AdoHcy hydrolase, while 3-deazaadenine maintained the inhibitory activity of the enzyme, indicating that N-7 is essential for its role as a hydrogen bonding acceptor. The substitution of hydrogen at the 6'-position with fluorine increased the inhibitory activity of the enzyme. The one-carbon homologation at the 5'-position generally decreased the inhibitory activity of the enzyme, indicating that steric repulsion exists. A molecular docking study also supported these experimental data. In this study, 6'-fluoroneplanocin A (2) was the most potent inhibitor of AdoHcy hydrolase (IC50 = 0.24 μM). It showed a potent anti-VSV activity (EC50 = 0.43 μM) and potent anticancer activity in all the human tumor cell lines tested.

Topics: Adenine; Adenosine; Adenosylhomocysteinase; Animals; Antineoplastic Agents; Antiviral Agents; Cell Line, Tumor; Chlorocebus aethiops; Enzyme Inhibitors; Humans; Molecular Docking Simulation; Neoplasms; Structure-Activity Relationship; Vero Cells; Virus Diseases; Viruses

Nucleoside phosphoramidates (NPs) are a class of nucleotide analogues that has been developed as potential antiviral/antitumor prodrugs. Recently, we have shown that some amino acid nucleoside phosphoramidates (aaNPs) can act as substrates for viral polymerases like HIV-1 RT. Herein, we report the synthesis and hydrolysis of a series of new aaNPs, containing either natural or modified nucleobases to define the basis for their differential reactivity. Aqueous stability, kinetics, and hydrolysis pathways were studied by NMR spectroscopy at different solution pD values (5-7) and temperatures. It was observed that the kinetics and mechanism (P-N and/or P-O bond cleavage) of the hydrolysis reaction largely depend on the nature of the nucleobase and amino acid moieties. Aspartyl NPs were found to be more reactive than Gly or β-Ala NPs. For aspartyl NPs, the order of reactivity of the nucleobase was 1-deazaadenine>7-deazaadenine>adenine>thymine≥3-deazaadenine. Notably, neutral aqueous solutions of Asp-1-deaza-dAMP degraded spontaneously even at 4 °C through exclusive P-O bond hydrolysis (a 50-fold reactivity difference for Asp-1-deaza-dAMP vs. Asp-3-deaza-dAMP at pD 5 and 70 °C). Conformational studies by NMR spectroscopy and molecular modeling suggest the involvement of the protonated N3 atom in adenine and 1- and 7-deazaadenine in the intramolecular catalysis of the hydrolysis reaction through the rare syn conformation.

Topics: Adenine; Amides; Amino Acids; Antiviral Agents; Crystallography, X-Ray; HIV-1; Kinetics; Magnetic Resonance Spectroscopy; Models, Theoretical; Molecular Conformation; Nucleosides; Phosphoric Acids; Prodrugs; Structure-Activity Relationship