Refernces
10.1016/j.tet.2008.01.133
The research focuses on the diastereoselective synthesis of D-xylo-isoxazolidinyl nucleosides, which are potentially active as antiviral and anticancer agents. The experiments involve the condensation of acetoxyisoxazolidines with silylated nucleobases such as uracil, thymine, cytosine, N-acetylcytosine, and guanine, using methods like the Vorbrüggen nucleosidation. The stereoselectivity of the addition depends on the structure of the substituent at C-3 from the starting chiral nitrone. The reactions were carried out under varying conditions, including different temperatures and solvents, to yield isoxazolidinyl b- and a-nucleosides with moderate to good stereoselectivity. The analyses used to determine the ratio of anomeric nucleosides, the stereochemistry, and the structure of the products included quantitative 13C NMR spectroscopy, NOE measurements, and mass spectrometry, with purification of the nucleosides achieved through flash column chromatography. The study also observed the formation of isoxazoline derivatives as side products under certain conditions and confirmed their structures using 2D NMR spectroscopy and chemical shift analysis.
10.1021/jo962204x
This research study on the synthesis and conformational analysis of cyclohexane nucleosides, specifically focusing on 3-hydroxy-4-(hydroxymethyl)-1-cyclohexanyl purines and pyrimidines. The purpose of the study was to understand the correlation between the antiviral activity of these compounds and their conformational structure. The researchers synthesized the nucleosides using various nucleobases and ethyl 1,3-cyclohexadiene-1-carboxylate through a conjugated addition reaction and hydroboration of the cyclohexenyl precursor. Key chemicals used in the synthesis process included adenine, 2-amino-6-chloropurine, thymine, uracil, cytosine, and various protecting groups like monomethoxytrityl and trityl groups, as well as reagents such as DBU, TFA, and BH3-THF complex. The lack of antiviral activity observed in the synthesized compounds was linked to their conformation, which was deduced from NMR and X-ray analysis. The study concluded that the replacement of the ring oxygen with a methylene group in carbocyclic nucleosides led to a change in the preferred conformation of the nucleoside base from axial to equatorial, which might explain the loss of antiviral activity compared to anhydrohexitol nucleosides.
10.1016/j.tet.2010.01.063
The research investigates the interactions between a series of novel bis-phenanthridinium–nucleobase conjugates and nucleotides. The study reveals that the adenine derivative of these conjugates exhibits high and selective affinity towards the complementary nucleotide UMP in an aqueous medium. This selective binding is attributed to specific changes in the UV–vis spectrum of phenanthridine subunits upon interaction with UMP, which differ significantly from changes caused by other nucleotides. Molecular modeling studies suggest that the stability and selectivity of the adenine-conjugate/UMP complex are correlated to the number of inter- and intramolecular aromatic stacking interactions between phenanthridinium subunits, covalently attached adenine, and added UMP. The selectivity is likely due to additional hydrogen bonding between UMP and adenine. Key chemicals involved in this research include bis-phenanthridinium–nucleobase conjugates, adenine, uracil, guanine, cytosine, and their respective nucleotides (AMP, UMP, GMP, CMP). The study also involves the use of various reagents such as tosyl chloride, pyridine, POCl3, NaOH, and DMF for the synthesis of the conjugates.
Xi,
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