Regioselective Reductive Opening of 4,6-O-Benzylidene Acetals of Glucose or Glucosamine Derivatives by BH3⋅Me2NH - BF3⋅OEt2

Abstract

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