A new access to enantiopure β-hydroxylated piperidines from N-Boc-2-acyloxazolidines.: Application to the synthesis of (-)-desoxoprosopinine and (+)-pseudoconhydrine

The synthesis of (-)-desoxoprosopinine and (+)-pseudoconhydrine were achieved from a common oxazolidine precursor. The three stereocenters present in (-)-desoxoprosopinine as well as the two stereocenters of (+)-pseudoconhydrine were created in highly stereoselective ways. The stereoselectivity observed during the reduction of the ketone moiety in the starting oxazolidine was dependent on the occurrence of a chelated intermediate. The others stereocenters arose from stereoselective reductions or alkylations of intermediate iminium ions. (C) 1998 Elsevier Science Ltd. All rights reserved.