Total Synthesis of (+)-<i>seco</i>-C-Oleanane via Stepwise Controlled Radical Cascade Cyclization
作者:Victoriano Domingo、Jesús F. Arteaga、José Luis López Pérez、Rafael Peláez、José F. Quı́lez del Moral、Alejandro F. Barrero
DOI:10.1021/jo201968t
日期:2012.1.6
of the (+)-seco-C-oleanane 1 was accomplished. The successful route to this natural product involves as the key step a stepwise regio- and stereocontrolled catalytic radical polyene cascadecyclization from preoleanatetraene oxide (16), a process mediated by Cp2TiCl. The use of this single-electron-transfer complex permits mild cyclization conditions without using unnecessary prefunctionalizations and
完成了(+)-癸基-C-油烷1的不对称简明全合成。通往这种天然产物的成功途径包括关键步骤,即由C12 Pc 2 TiCl介导的由预油萘四烯氧化物(16)进行的区域和立体控制的催化自由基多烯级联环化反应。这种单电子转移配合物的使用允许温和的环化条件,而无需使用不必要的预官能化,并在双环水平上停止了该过程。理论数据表明,第三环闭合具有很高的活化能,这将说明环化作用的控制。此过程还导致天然(-)-山茱ach醇B,山茶酚A和(+)-山梨醇-β-amyrin为次要化合物。
First Total Synthesis of (−)-Achilleol B: Reassignment of Its Relative Stereochemistry
作者:Jesús F. Arteaga、Victoriano Domingo、José F. Quílez del Moral、Alejandro F. Barrero
DOI:10.1021/ol800326n
日期:2008.5.1
The first totalsynthesis of (-)-achilleol B was achieved using a convergent approach with a longest linear sequence of 14 steps. Three key steps were employed, including an enantioselective Robinson annelation for the construction of the bicyclic moiety. The monocyclic synthon was prepared through a Ti(III)-mediated cylization of a chiral monoepoxide obtained via asymmetric dihydroxylation of geranylacetone
Enantioselective Annulation Using Nazarov Reagent: Synthesis of (+)-Preoleanatetraene
作者:Alejandro F. Barrero、Simeón Arseniyadis、José F. Moral、M. Mar Herrador、Antonio Rosellón
DOI:10.1055/s-2005-864798
日期:——
The enantioselective synthesis of preoleanatetraene (1) has been accomplished via a convergent approach of two C-15 synthons. The key step of this synthesis has been an interesting enantioselective variant of the Robinson annulation using the Nazarov reagent and a chiral enamine to obtain the bicyclic moiety A. This asymmetric methodology opens the access to other irregular triterpene skeletons whose biogenetic implication should not be underestimated.