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DOI: 10.1055/s-1999-3398
Diastereo- and Enantioselective Formal Synthesis of (+)-Conagenin via Asymmetric [2,3]-Wittig Rearrangement
Publication History
Publication Date:
31 December 1999 (online)
![](https://www.thieme-connect.de/media/synthesis/199902/lookinside/thumbnails/10.1055-s-1999-3398-1.jpg)
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