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.