Stereocontrolled synthesis of pyrrolidine iminosugars through asymmetric dihydroxylation reaction
Iminosugars are carbohydrate analogues in which the endocyclic oxygen is replaced by a nitrogen atom [1]. These compounds are nowadays the most attractive class of sugar mimics because of their high glycosidase and glycosyltransferase inhibitor activity and hence their therapeutic potential in a vast array of diseases [2]. The synthetic key step in our approach for preparation of some classes of iminosugars, is the asymmetric dihydroxylation reaction (AD). In this work we conducted a systematic study about AD reaction on the unsaturated azido alchohols 1 and 2 identified in our precedent studies as the ideal precursors of pyrrolidine ring [3] (Scheme 1). Scheme 1 The conditions were optimized in order to modulate the diastereomeric ratio of the diols depending on which Cinchona type chiral ligand was used, thus allowing to obtain four adjacent stereocentres with full stereochemistry control.