C-Arylglucoside synthesis:: triisopropylsilane as a selective reagent for the reduction of an anomeric C-phenyl ketal

Reduction of tetra-O-benzyl-protected 1C-phenylglucoside using triethylsilane and (BF3OEt2)-O-. has been reported (Czernecki. S.: Ville. G. J. Org. Chem. 1989, 54, 610-612) to give exclusively 2,3,4,6-tetra-a-O-benzyl-beta-1C-phenyl-1-deoxyglucoside. We have determined that this reduction actually gives a 4:1 mixture of anomers (beta:alpha). We observed that the selectivity of the reduction is influenced by the steric bulk of the silane. The use of triisopropylsilane as a reducing agent gives >35:1 ratio (beta:alpha) of 2.3.4.6-tetra-O-benzyl-beta-1C-phenyl-1-deoxyglucoside. (C) 2003 Elsevier Ltd. All rights reserved.