Design, synthesis, and applications of new oxygenated chiral auxiliaries

Abstract

The magnesium bromide etherate-mediated addition of allyltributyltin to an a-alkoxyaldehyde bearing a protected 3-hydroxytetrahydropyranyl- moiety was shown to be highly diastereoselective. The sense and the level of induction depend on the nature of the protecting group at C-3. Esters and benzyl ether gave the opposite relative stereochemistry in comparison to silyl ethers. It was also found that the other enantiomer of an optically active 1, 2-diol could be obtained using the same chiral auxiliary simply by changing the stereochemistry at the anomeric position. The exceptionally high level of 1, 4-induction in these systems was attributed to the formation of a tridentate chelate involving one oxygen atom of the auxiliary and both oxygen atoms of the aglycone. © 1992, Walter de Gruyter. All rights reserved.