Dramatic influence of ester steric hindrance on the diastereoselectivity of a Michael addition towards the synthesis of the ABC tricycle of hexacyclinic acid
作者:Alexandre Audic、Raphaël Oriez、Joëlle Prunet
DOI:10.1016/j.tet.2020.131843
日期:2021.1
During our studies toward the synthesis of the ABC ring system of hexacyclinic acid, we observed an unexpected influence of the steric bulk of the ester group of the Michael acceptor in a key conjugate addition. We propose an eight-membered ring transition state to explain the formation of the undesired diastereomer in the case of unhindered esters.
Synthesis of C1–C20 and C21–C40 fragments of tetrafibricin
作者:Venugopal Gudipati、Dennis P. Curran
DOI:10.1016/j.tetlet.2011.01.086
日期:2011.4
Efficient syntheses of suitably functionalized top and bottom fragments of tetrafibricin are described. The bottom fragment is prepared by two consecutive Kocienski-Julia couplings, while the top fragment synthesis features a dithiane alkylation and a Horner-Wadsworth-Emmons reaction. (C) 2011 Elsevier Ltd. All rights reserved.
Dramatic Solvent Effect on the Diastereoselectivity of Michael Addition: Study toward the Synthesis of the ABC Ring System of Hexacyclinic Acid
作者:Julie Toueg、Joëlle Prunet
DOI:10.1021/ol702566c
日期:2008.1.1
During our studies toward the synthesis of the ABC ring system of hexacyclinic acid, we have observed a dramatic influence of the solvent on both our key steps. The diastereoselectivity of the intermolecular Michael addition could be totally reversed by changing the polarity of the solvent, and trifluoroethanol was found to be the optimal solvent for the following Mn(III)-promoted radical cyclization.
Two dienes comprising the complete heavy-atom framework of the macrocyclic core of the marine macrolide leiodolide A were prepared by esterification of an appropriate carboxylic acid and two alcohol building blocks. The latter were obtained in a stereoselective fashion from ( R )-citronellal via a Crimmins-type aldol reaction, oxidative double bond cleavage, and efficient oxazole formation as the key
包含海洋大环内酯类碘内酯 A 的大环核心的完整重原子骨架的两种二烯是通过适当的羧酸和两种醇结构单元的酯化反应制备的。后者是通过 Crimmins 型羟醛反应、氧化双键断裂和有效恶唑形成作为关键转化从 ( R )-香茅醛以立体选择性方式获得的。在不同条件下研究了可能的基于闭环复分解 (RCM) 的二烯大环化。在任何这些实验中都没有获得环化产物,因此表明 C6 和 C7 之间的 RCM 可能不是 leiodolide A 全合成的可行策略。
α-EWG-Substituted Enones: Suitable Substrates for Ring-Closing Metathesis
作者:Julie Toueg、Joëlle Prunet
DOI:10.1055/s-2006-950274
日期:2006.10
The A-ring of hexacyclinic acid has been synthesised, using a ring-closing metathesis involving an α-EWG-substituted enone as the key step. We have then explored the scope of this reaction, which gives access to various 5- and 6-membered rings.