A Straightforward and Flexible [4 + 2] Route to β-C-Naphthyl-2-deoxy-glycosides through Tandem Hydroboration-Ketal Reduction: De Novo Access to C-Naphthyl-6-fluoro and 6,6-Difluoro 2-Deoxyglycosides
journal contributionposted on 01.04.2005, 00:00 by Nguyen Quang Vu, Stéphane Leconte, Eric Brown, Danielle Grée, René Grée, Gilles Dujardin
Under standard hydroboration-oxidation conditions, the dihydropyrans 4 underwent a highly stereocontrolled tandem reaction, involving the expected hydration of the double bond together with the reduction of the ketal moiety. This unprecedented transformation gives rise to a short, [4 + 2]-based synthetic route to (±)-β-C-naphthyl-2-deoxyglycosides 5, which allows a significant structural and functional diversity at C-6. We thus described the first synthesis of (±)-C-aryl-6-fluoro and -6,6-difluoro olivosides, via the allylic mono- and difluorides produced by regioselective fluorination of, respectively, hydroxyalkyl and oxoalkyl dihydropyran derivatives.