title: Synthesis of 2'-C-difluoromethylribonucleosides and their enzymatic incorporation into oligonucleotides.
abstract: [Chemical reaction: See text] Nucleosides 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-beta-difluoromethylribonucleosides. We constructed the glycosylating agent 4 in three steps from 1,3,5-tri-O-benzoyl-alpha-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-alpha-difluoromethyl-arabino-alpha-pyrimidine. To incorporate 2'-C-beta-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.
authors.affiliation: Howard Hughes Medical Institute, Department of Biochemistry & Molecular Biology, University of Chicago, Illinois 60637, USA.
authors.forename: Jing-Dong
authors.initials: JD
authors.lastname: Ye
authors.forename: Xiangmin
authors.initials: X
authors.lastname: Liao
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Piccirilli
mesh_terms: D001483:Base Sequence; D005459:Fluorides; D008745:Methylation; D008958:Models, Molecular; D008968:Molecular Conformation; D009841:Oligonucleotides / Q000096:biosynthesis* / Q000737:chemistry; D011743:Pyrimidines / Q000138:chemical synthesis; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D012263:Ribonucleosides / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D009841:Oligonucleotides; D011743:Pyrimidines; D012263:Ribonucleosides; D012313:RNA; D005459:Fluorides