Fifteen steps suffice for an enantioselective total synthesis of (-)-strychnine (1) from 1,3-cyclohexanedione. The key steps are the easy generation of the enantiopure intermediate 2, the closure of the piperidine ring by a reductive Heck reaction, and the elaboration of the indoline nucleus in an advanced synthetic stage. TBDMS=tert-butyldimethylsilyl.
A Novel and General Synthetic Pathway to Strychnos Indole Alkaloids: Total Syntheses of (−)-Tubifoline, (−)-Dehydrotubifoline, and (−)-Strychnine Using Palladium-Catalyzed Asymmetric Allylic Substitution
作者:Miwako Mori、Masato Nakanishi、Daisuke Kajishima、Yoshihiro Sato
DOI:10.1021/ja029382u
日期:2003.8.1
recrystallized from EtOH to give an optically pure compound. From this compound, tetracyclic ketone 13, which should be a useful intermediate for the synthesis of indole alkaloids, could be synthesized. The total syntheses of (-)-dehydrotubifoline, (-)-tubifoline, and (-)-strychnine were achieved from 13. All ring constructions for the syntheses of these natural products were achieved using a palladium catalyst
Approaches to the Synthesis of (±)-Strychnine via the Cobalt-Mediated [2 + 2 + 2] Cycloaddition: Rapid Assembly of a Classic Framework
作者:Michael J. Eichberg、Rosa L. Dorta、Douglas B. Grotjahn、Kai Lamottke、Martin Schmidt、K. Peter C. Vollhardt
DOI:10.1021/ja016333t
日期:2001.9.1
Five synthetic approaches to racemic strychnine (1), with the cobalt-mediated [2 + 2 + 2] cycloaddition of alkynes to indoles as the key step, are described. These include the generation and attempted cyclization of macrocycle 8 and the synthesis of dihydrocarbazoles 15, 22, and 26 and their elaboration to pentacyclic structures via a conjugate addition, dipolarcycloaddition, and propellane-to-spirofused
The Formal Total Synthesis of (±)-Strychnine via a Cobalt-Mediated [2 + 2 + 2]Cycloaddition
作者:Michael J. Eichberg、Rosa L. Dorta、Kai Lamottke、K. Peter C. Vollhardt
DOI:10.1021/ol006131m
日期:2000.8.1
A short, highly convergent totalsynthesis of racemic isostrychnine, and thus strychnine, has been completed. The route involves 14 steps in the longest linear sequence and is highlighted by a cobalt-mediated [2 + 2 + 2]cycloaddition of an alkynylindole nucleus to acetylene.
Strychnos alkaloids have attracted a great deal of attention from synthetic chemists. Herein, we describe the concise asymmetric totalsyntheses of the Strychnos alkaloids, (−)-dehydrotubifoline, (−)-tubifoline, and (−)-tubifolidine, as well as the formal total synthesis of (−)-strychnine. Our strategy features the construction of the common tetracyclic pyrrolo[2,3-d]carbazole structure using regioselective