From d-glucuronic acid to l-iduronic acid derivatives via a radical tandem decarboxylation–cyclization

• l-Idose derivatives useful in antithrombotic oligosaccharides are prepared.
• Radical formation at C-5 of d-glucuronic is achieved by Barton decarboxylation.
• Cyclization on a propargylic tether at O4 gave complete stereoselectivity toward l-idose.

A synthesis to l-iduronic derivatives, major components of heparin derived pentasaccharides was accomplished by formal inversion of configuration at C-5 of a d-glucuronic acid derivative through radical formation at C-5 using Barton decarboxylation followed by intramolecular radical addition on an acetylenic tether at O-4 giving exclusively a bicyclic sugar of l-ido configuration. Oxidation and ring opening of this bicyclic sugar led to a l-iduronate. This method opens the way to short syntheses of pentasaccharidic moiety of Idraparinux and congeners.

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