Concise Synthesis of Furanosyl Benzimidazole C-Nucleosides by Mitsunobu Reaction

Tetri/pentitolyl benzimidazoles were prepared by using the unprotected monosaccharides and o-phenylenediamine as the starting materials. Intramolecular dehydration of the oligotoltyl benzimidazoles afforded two furanosyl benzimidazole C-nucleosides (alpha/beta isomers) through Mitsunoble reaction. One isomer was the configuration-retension product, the other was the configuration-inversion one. The regioselectivity of Mitsunobu reaction is good, which provides an effective protocol for the synthesis of furanosyl benzimidazole C-nucleosides.