Download MendeleyStructural Basis of Duplex Thermodynamic Stability and Enhanced Nuclease Resistance of 5'-C-Methyl Pyrimidine-Modified Oligonucleotides.
Kel In, A.V., Zlatev, I., Harp, J., Jayaraman, M., Bisbe, A., O Shea, J., Taneja, N., Manoharan, R.M., Khan, S., Charisse, K., Maier, M.A., Egli, M., Rajeev, K.G., Manoharan, M.(2016) J Org Chem 81: 2261-2279
- PubMed: 26940174
- DOI: https://doi.org/10.1021/acs.joc.5b02375
- Primary Citation of Related Structures:
5D8T, 5DEK, 5DER - PubMed Abstract:
Although judicious use of chemical modifications has contributed to the success of nucleic acid therapeutics, poor systemic stability remains a major hurdle. The introduction of functional groups around the phosphate backbone can enhance the nuclease resistance of oligonucleotides (ONs). Here, we report the synthesis of enantiomerically pure (R)- and (S)-5'-C-methyl (C5'-Me) substituted nucleosides and their incorporation into ONs. These modifications generally resulted in a decrease in thermal stability of oligonucleotide (ON) duplexes in a manner dependent on the stereoconfiguration at C5' with greater destabilization characteristic of (R)-epimers. Enhanced stability against snake venom phosphodiesterase resulted from modification of the 3'-end of an ON with either (R)- or (S)-C5'-Me nucleotides. The (S)-isomers with different 2'-substituents provided greater resistance against 3'-exonucleases than the corresponding (R)-isomers. Crystal structure analyses of RNA octamers with (R)- or (S)-5'-C-methyl-2'-deoxy-2'-fluorouridine [(R)- or (S)-C5'-Me-2'-FU, respectively] revealed that the stereochemical orientation of the C5'-Me and the steric effects that emanate from the alkyl substitution are the dominant determinants of thermal stability and are likely molecular origins of resistance against nucleases. X-ray and NMR structural analyses showed that the (S)-C5'-Me epimers are spatially and structurally more similar to their natural 5' nonmethylated counterparts than the corresponding (R)-epimers.
Organizational Affiliation:
Alnylam Pharmaceuticals , 300 Third Street, Cambridge, Massachusetts 02142, United States.
