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Obtention sélective de diènes 5,7 stéroides : eproduits à visée thérapeutique

Abstract : The study concerns the optimization of 2 steps in the industrial preparation of steroids 5,7 dienes.The allylic bromination of cholesteryl acetate gives the 2 epimers 7- et 7-bromo (85 %, ratio 7/7-Br AcC 65/35). Knowing that the epimer 7 provides the 5,7 diene by dehydrobromination, the objective was to obtain it mainly. Thus, an epimerization was conducted, by adding a bromide salt, soluble in the middle issued from the bromination, to achieve a 7/7-Br AcC ratio of 90/10. The dehydrobromination, in the industrial conditions, uses collidine in toluene at reflux (5,7 / 4,6 70/30 maximum). The 4,6 diene quantity is important, moreover the reaction temperature does not allow to keep the benefit of the epimerization. An alternative process is to use tetrabutylammonium fluoride that gives a better selectivity : prevalent formation of 5,7 diene (80 %, 5,7 / 4,6 ratio 99/1, starting from 7-Br AcC) with correctly dried TBAF
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Submitted on : Thursday, March 29, 2018 - 1:38:37 PM
Last modification on : Friday, September 25, 2020 - 2:36:43 PM

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  • HAL Id : tel-01752212, version 1



Luc Selve. Obtention sélective de diènes 5,7 stéroides : eproduits à visée thérapeutique. Autre. Institut National Polytechnique de Lorraine, 2003. Français. ⟨NNT : 2003INPL070N⟩. ⟨tel-01752212⟩



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