3.13 Carbohydrate Derived Auxiliaries: Amino Sugar and Glycosylamine Auxiliaries

The stereodifferentiating potential of carbohydrate auxiliaries is illustrated by examples of oxazolidinones derived from amino sugars and aldimines of glycosylamines. Taking advantage of the bicyclic structure of amino sugar-derived oxazolidinones, reactions of their unsaturated or deprotonated N -acyl derivatives show an efficient exo - versus endo -differentiation. High diastereoselectivity is achieved in the syntheses of β -branched or α -substituted carboxylic acid derivatives. Imines of glycosylamines, in particular of 2,3,4,6-tetra- O -pivaloyl- β - d -galactopyranosylamine, are characterized by a conformation stabilized through the exo -anomeric effect and by their ability to coordi…