4′‑C‑Methoxy-2′-deoxy-2′-fluoro Modified Ribonucleotides Improve Metabolic Stability and Elicit Efficient RNAi-Mediated Gene Silencing

• Published in: Journal of the American Chemical Society Vol. 139; no. 41; pp. 14542 - 14555
• Main Authors: Malek-Adamian, Elise, Guenther, Dale C, Matsuda, Shigeo, Martínez-Montero, Saúl, Zlatev, Ivan, Harp, Joel, Burai Patrascu, Mihai, Foster, Donald J, Fakhoury, Johans, Perkins, Lydia, Moitessier, Nicolas, Manoharan, Rajar M, Taneja, Nate, Bisbe, Anna, Charisse, Klaus, Maier, Martin, Rajeev, Kallanthottathil G, Egli, Martin, Manoharan, Muthiah, Damha, Masad J
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 18.10.2017; Amer Chemical Soc; American Chemical Society (ACS)
• Subjects: 60 APPLIED LIFE SCIENCES; Chemistry; Chemistry, Multidisciplinary; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Physical Sciences; Science & Technology; 4-SUBSTITUTED NUCLEOSIDES; OLIGODEOXYNUCLEOTIDES; CIRCULAR-DICHROISM; AFFINITY; INTERFERENCE; CONFORMATIONAL-ANALYSIS; SIRNA; POTENTIALS; NUCLEASE RESISTANCE; OLIGONUCLEOTIDES
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b07582

We designed novel 4′-modified 2′-deoxy-2′-fluorouridine (2′-F U) analogues with the aim to improve nuclease resistance and potency of therapeutic siRNAs by introducing 4′-C-methoxy (4′-OMe) as the alpha (C4′α) or beta (C4′β) epimers. The C4′α epimer was synthesized by a stereoselective route in six steps; however, both α and β epimers could be obtained by a nonstereoselective approach starting from 2′-F U. 1H NMR analysis and computational investigation of the α-epimer revealed that the 4′-OMe imparts a conformational bias toward the North-East sugar pucker, due to intramolecular hydrogen bonding and hyperconjugation effects. The α-epimer generally conceded similar thermal stability as unmodified nucleotides, whereas the β-epimer led to significant destabilization. Both 4′-OMe epimers conferred increased nuclease resistance, which can be explained by the close proximity between 4′-OMe substituent and the vicinal 5′- and 3′-phosphate group, as seen in the X-ray crystal structure of modified RNA. siRNAs containing several C4′α-epimer monomers in the sense or antisense strands triggered RNAi-mediated gene silencing with efficiencies comparable to that of 2′-F U.