Modular Synthesis of 5‐Substituted Furan‐2‐yl C‐2′‐Deoxyribonucleosides and Biaryl Covalent Base‐Pair Analogues

A modular and efficient synthesis of 5-(hetero)arylfuran C-2'-deoxyribonucleosides was developed. Friedel-Crafts C-glycosidation of 2-bromofuran with toluoyl-protected methyl 2'-deoxyribofuranoside in the presence of BF 3 ·Et 2 O gave 5-bromofuran C-nucleosides, which were used as key intermediates for Stille or Suzuki coupling with (hetero)arylstannanes or boronic acids to afford a series of 5-(hetero)arylfuran C-nucleosides. 5-Boronofuran C-nucleoside was prepared by the Suzuki coupling of bromofuran with bis(pinacolatodiboron) or by Ir-catalyzed C―H borylation of furan and was used for cross-coupling with 5-bromoheteroaryl C-nucleosides to furnish novel covalent analogues of nucleoside pairs. The title 5-arylfuran C-nucleosides possess interesting fluorescence properties that may be applicable for fluorescent labeling of biomolecules.