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Synthesis of 2‘-C-Difluoromethylribonucleosides and Their Enzymatic Incorporation into Oligonucleotides
journal contribution
posted on 2005-09-30, 00:00 authored by Jing-Dong Ye, Xiangmin Liao, Joseph A. PiccirilliNucleosides bearing a branched ribose have significant promise as therapeutic agents and
biotechnological and biochemical tools. Here we describe synthetic entry into a new subclass of
these analogues, 2‘-C-β-difluoromethylribonucleosides. We constructed the glycosylating agent 4
in three steps from 1,3,5-tri-O-benzoyl-α-d-ribofuranose 1. The key steps included nucleophilic
addition of difluoromethyl phenyl sulfone to 2-ketoribose 2 followed by mild and efficient reductive
desulfonation. Ribofuranose 4 glycosylated bis(trimethylsilyl)uracil directly, giving difluoromethyluridine 7 efficiently after deprotection. Conversion of 4 to the corresponding ribofuranosyl bromide
allowed efficient access to C, A, and G analogues. A related approach starting from methyl
d-ribofuranose offered synthetic entry into the diastereomeric manifold, 2‘-C-α-difluoromethyl-arabino-α-pyrimidine. To incorporate 2‘-C-β-difluoromethyluridine into an oligodeoxynucleotide we
converted 7 to the bisphosphate and carried out successive ligation reactions using T4 RNA ligase
and T4 DNA ligase. Analogous to natural RNA linkages, the resulting oligonucleotide undergoes
hydroxide-catalyzed backbone scission at the difluoromethyluridine residue via internal transphosphorylation.
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nucleophilic additiondifluoromethyl phenyl sulfoneRNA linkagesdiastereomeric manifoldOligonucleotides Nucleosidesdifluoromethyluridine residueT 4 DNA ligaseligation reactionsdifluoromethyluridine 7G analoguesglycosylating agent 4ribofuranosyl bromidereductive desulfonationEnzymatic IncorporationT 4 RNA ligaseentry
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