Cobalt‐Catalyzed Hydrogen‐Atom Transfer Induces Bicyclizations that Tolerate Electron‐Rich and Electron‐Deficient Intermediate Alkenes
作者:Darius Vrubliauskas、Christopher D. Vanderwal
DOI:10.1002/anie.202000252
日期:2020.4.6
hexafluoroisopropanol as the solvent. The process is presumably initiated by metal‐catalyzed hydrogen‐atom transfer (MHAT) to 1,1‐disubstituted or monosubstituted alkenes, and the reaction is remarkable for its tolerance of internal alkenes bearing either electron‐rich methyl or electron‐deficient nitrile substituents. Electron‐rich aromatic terminators are required in both cases. Terpenoid scaffolds
开发了一种新型 Co II催化的多烯环化,该环化在六氟异丙醇作为溶剂中进行时特别有效。该过程可能是通过金属催化氢原子转移(MHAT)至1,1-二取代或单取代烯烃引发的,并且该反应因其对带有富电子甲基或缺电子腈取代基的内部烯烃的耐受性而引人注目。这两种情况都需要富电子芳香族终止剂。具有不同取代模式的萜类支架具有优异的非对映选择性,并制备了具有生物活性的C20氧化松香烷二萜鼠尾草醛以展示含腈产品的实用性。还提供了几个机械实验的结果,表明该过程的特点是 MHAT 诱导的自由基双环化和后期氧化以再生芳香族终止剂。
Enantio- and Diastereoselective Stepwise Cyclization of Polyprenoids Induced by Chiral and Achiral LBAs. A New Entry to (−)-Ambrox, (+)-Podocarpa-8,11,13-triene Diterpenoids, and (−)-Tetracyclic Polyprenoid of Sedimentary Origin
stepwise cyclization of polyprenoids induced by Lewis acid-assisted chiral Brønsted acids (chiral LBAs) and achiral LBAs is described. In particular, the absolute stereocontrol in the initial cyclization of polyprenoids to form an A-ring induced by chiral LBAs and the importance of the nucleophilicity of the internal terminator in polyprenoids for the relative stereocontrol in subsequent cyclization are
Zur Kenntnis der Diterpene. 57. Mitteilung. Die Konstitution der Agathendisäure
作者:L. Ruzicka、R. Zwicky、O. Jeger
DOI:10.1002/hlca.19480310735
日期:——
12-Tetra-methyl-octahydro-phenanthren (XI) herstellen, wodurch die identische Struktur und Konfiguration der Ringe A und B bei I und XII bewiesen wurde. Da bereits früher gleiche Zusammenhänge zwischen dem Manool und der tricyclischen Abietinsäure (XVI) gefunden werden konnten, besitzt die Agathendisaure die gleiche Verknüpfung der Ringe A und B wie die Abietinsäure.
Ausgehend von den bicyclischen DiterpenverbindungenAgathendisäure(I)和Manool(XII)位于sich das gleiche 1,1,7,12-四甲基-八氢菲-蒽(XI)的零星,独特的结构我和XII变成了世界末日。由德国国家安全局(XVI)和德国联邦储备银行(BVI)共同资助,由德国联邦政府和美国联邦政府担保。
Highly Efficient Synthesis of (+)-Nimbiol and Other Podocarpanes Derivatives from Sclareol
A new access to tricyclic diterpenes of podocarpane skeleton has been opened, in excellent overall yields, and an efficient synthesis of (+)-nimbiol from sclareol has been achieved.
d-Kaurene (XXXVI) and d-phyllocladene (XXXVII) were synthesized from l-abietic acid (I) via intramolecular carbenoid reaction of diazoketones and subsequent cleavage of the resulting cyclopropyl ring with Li-liq. NH3. Methyl dehydroabietate (XVI) and dehydroabietane (V) introduced from I were used as the starting materials. The improved synthesis of V was also described.
d-Kaurene (XXXVI)和 d-phyllocladene (XXXVII)是由 l-阿松香酸 (I) 通过重氮酮的分子内类羰基反应合成的,随后用 Li-liq.NH3。脱氢阿比特酸甲酯 (XVI) 和从 I 引入的脱氢阿比特烷 (V) 被用作起始原料。此外,还介绍了 V 的改进合成方法。