Download PDF
Synthesis 1999; 1999(2): 243-248
DOI: 10.1055/s-1999-3398
paper
© Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published therein, is legally protected by copyright for the duration of the copyright period. Any use, exploitation or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, is illegal and liable to criminal prosecution. This applies in particular to photostat reproduction, copying, cyclostyling, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

Diastereo- and Enantioselective Formal Synthesis of (+)-Conagenin via Asymmetric [2,3]-Wittig Rearrangement

Dieter Enders* , Michael Bartsch, Jan Runsink
  • *Institut für Organische Chemie, Rheinisch-Westfälische Technische Hochschule, Professor-Pirlet-Straße 1, D-52074 Aachen, Germany; Fax +49(2 41)8 88 81 27; E-mail: Enders@RWTH-Aachen.de
Further Information

Publication History

Publication Date:
31 December 1999 (online)

  PDF Download  Permissions and Reprints All articles of this category

The formal synthesis of the immunomodulator (+)-conagenin (1) is accomplished in a twelve-step sequence with good overall yield (19%), diastereoselectivity and enantiomeric excess (ds syn = 88%, ee = 91%). Key steps of the synthesis are the asymmetric [2,3]-Wittig rearrangement of crotyloxyacetaldehyde-SAEP-hydrazone (S)-5 and the diastereoselective reduction of methylketone (R,S)-12. The absolute configuration of the (4R)-stereogenic center was determined by 1H NMR NOE-measurements with respect to the known absolute configuration of the (2R,3S)-stereogenic centers of lactone (R,S,R)-14.

conagenin - immunomodulator - [2,3]-Wittig rearrangement - chiral hydrazone - asymmetric synthesis

      >