129390-49-4Relevant articles and documents
Enantiomerically pure polyhydroxylated acyliminium ions. Synthesis of the glycosidase inhibitors (-)-swainsonine and (+)-castanospermine
Miller, Scott A.,Chamberlin, A. Richard
, p. 8100 - 8112 (2007/10/02)
Hydroxylactams, which are useful precursors of acyl iminium ions for cationic cyclization, are most often prepared by hydride reduction of imides. This procedure is not directly applicable, however, to the enantioselective preparation of any highly substituted hydroxy lactam that would be derived from a meso imide, since such a reduction with the usual achiral agents must produce a racemic product. Two enantioselective methods of preparing representative examples of this type of substituted hydroxylactam have therefore been explored. Reduction of a meso imide with a number of enantiomerically pure chiral reducing agents has been found to give up to 56% ee of the corresponding hydroxylactam. Much higher levels of enantiomeric purity are readily obtainable by direct synthesis from monosaccharide lactones derived from either ribose or lyxose, affording either enantiomeric series of hydroxy lactams, (+)-9α, 14-16, and (-)-9α, 20-23, respectively. One such hydroxylactam, 23 has been converted into the mannosidase inhibitor (-)-swainsonine via a synthetic route that features a novel multiple reduction of a vinylogous N-acylurethane to establish the correct ring juncture stereochemistry. Extension of the monosaccharide strategy to the enantioselective synthesis of six-membered-ring hydroxylactams also allows a facile preparation of 29, leading to the glucosidase inhibitor (+)-castanospermine and the new indolizidine alkaloid 1,8a-diepicauistanospermine.
