Highly Stereoselective Grignard Reaction of an Aldopyranose : A Simple synthesis of 6-Deoxy-D-idose from D-Xylose

Abstract

Grignard reaction of 2, 3, 4-tri-O-benzyl-D-xylopyranose yielded a single product with very high stereoselectivity. A threo relationship of the newly created chiral center with respect to C₂ was established by converting the product into the δ-lactone of D-ido configuration, then to the unsaturated lactone of threo configuration. The result made possible a stereoselective synthesis of 6-deoxy-D-idose from D-xylose in a small number of steps. Models accounting for the high stereoselectivity in the Grignard reaction of aldoses are discussed.