2'-Spiro ribo- and arabinonucleosides: synthesis, molecular modelling and incorporation into oligodeoxynucleotides.
We have synthesized four conformationally restricted bicyclic 2'-spiro nucleosides via 2'-C-allyl nucleosides as key intermediates. The ribo-configured 2'-spironucleosides 9b and 14b were obtained by a convergent strategy starting from 2-ketofuranose 1 whereas the arabino-configured 2'-spironucleosides 21 and 27 were obtained by a linear strategy with a 2'-ketouridine derivative as starting material. The furanose ring of 9b/14b adopts N-type conformations whereas the furanose ring of 21/27 exists as an N<==>S equilibrium. These compounds showed no anti-HIV-1 activity or cytotoxicity. Incorporation of the four 2'-spironucleosides (as monomers X4 and X5) into oligodeoxynucleotides was accomplished using the phosphoramidite approach on an automated DNA synthesizer. Irrespective of monomeric configuration, hybridization studies revealed that these 2'-spironucleotide monomers (X4 and X5) induce decreased duplex thermostabilities compared with the corresponding DNA:DNA and DNA:RNA duplexes. Molecular modelling indicated that steric constraints are a possible reason for the lowered binding affinities of the modified oligodeoxynucleotides towards complementary single-stranded DNA and single-stranded RNA complements.
Nucleic Acid Center, Department of Chemistry, University of Southern Denmark, DK-5230 Odense M, Denmark.
B Ravindra
BR
Babu
Lise
L
Keinicke
Michael
M
Petersen
Claus
C
Nielsen
Jesper
J
Wengel
D019380:Anti-HIV Agents / Q000138:chemical synthesis* / Q000737:chemistry; D001087:Arabinonucleosides / Q000138:chemical synthesis / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry*; D012313:RNA / Q000737:chemistry; D013141:Spiro Compounds / Q000138:chemical synthesis / Q000737:chemistry
D019380:Anti-HIV Agents; D001087:Arabinonucleosides; D009838:Oligodeoxyribonucleotides; D013141:Spiro Compounds; D012313:RNA; D004247:DNA