A Fast and Effective Hydrogenation Process of Protected Pentasaccharide: A Key Step in the Synthesis of Fondaparinux Sodium

An improved method for the simultaneous removal of O-benzyl and N-carboxybenzyl groups as well as reducing azide groups to amines in protected heparin-like pentasaccharides, a key process in fondaparinux sodium synthesis, is reported. Under catalytic transfer hydrogenation conditions, using readily available and inexpensive ammonium formate, the hydrogenolysis is done in less than an hour in good yield and purity. This procedure represents a major advantage over the previously published procedures, the latter of which involve several hours/days of hydrogenation reaction under catalytic reduction using gaseous hydrogen.