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Synthèse de Hoodigogénine A, aglycone de glycostéroïdes extraits de Hoodia gordonii : vers la synthèse des 14β-hydroxy androstanes et /ou des 14β-hydroxy prégnanes

Abstract : This thesis is dealing with the synthesis of a glycosteroid named P57 extracted from Hoodia gordonii, a succulent plant known for its appetite suppressant properties. The first part of this work describes the synthesis of the hoodigogenin A, the aglycon of the P57. The key step of this synthesis was a Norrish type I reaction combined with a Prins reaction leading to the introduction of a 14β-hydroxyl function starting from the corresponding 12-keto steroids. The studies showed that the A/B ring junction has no influence on the Norrish type I-Prins reaction but that the substitution pattern at position 20 is important. Thus, the synthesis of the hoodigogenin A was realized for the first time in 13 steps with 3% global yield starting from the 3α-12α-diacetoxypregnanone and this methodology also allowed us to synthesize three analogs of the hoodigogenin A. The second part deals with the total synthesis of 14β-hydroxy-androstanes. In order to access to a bicyclic derivative representing cycles C and D of steroids, we worked on an intramolecular Michael-aldol reaction promoted by TiCl4. The extension of this Michael-aldol reaction afforded very efficiently a large variety of polyfunctionalized 5-5, 5-6 and 6-6 fused ring systems. Then, a Diels-Alder reaction from a 1,3- diene obtained from a hydrindenon derivative led us to a first tetracyclic compound bearing a 14β-hydroxyl function. Finally, two other tetracyclic derivatives had been obtained by a Michael reaction followed by a Robinson reaction.
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Blandine Ressault. Synthèse de Hoodigogénine A, aglycone de glycostéroïdes extraits de Hoodia gordonii : vers la synthèse des 14β-hydroxy androstanes et /ou des 14β-hydroxy prégnanes. Autre. Université de Strasbourg, 2012. Français. ⟨NNT : 2012STRAF067⟩. ⟨tel-00940453⟩

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