Diastereo- and Enantioselective Formal Synthesis of (+)-Conagenin via Asymmetric [2,3]-Wittig Rearrangement
- 1 February 1999
- journal article
- research article
- Published by Georg Thieme Verlag KG in Synthesis
- Vol. 1999 (02) , 243-248
- https://doi.org/10.1055/s-1999-3398
Abstract
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.Keywords
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