REGIOSELECTIVE REDUCTIVE OPENING OF 4,6-O-BENZYLIDENE ACETALS OF GLUCOSE OR GLUCOSAMINE DERIVATIVES BY BH3-ME(2)NH-BF3-OET(2)

Here described is the reduction of 4,6-O-benzylidene functionalities o f D-glucose or D-glucosamine with various protecting groups by borane dimethylamine complex and boron trifluoride etherate. The 4-O-benzyl p roducts were selectively obtained when the reaction was carried out in dichloromethane for substrates with 3-O-benzyl groups. In contrast, t he reaction in acetonitrile provided the 6-O-benzyl products predomina ntly for substrates 3-O-protected in other forms than a benzyl ether.