For decades, akuammiline alkaloids have attracted synthetic chemists due to their intriguing molecular architecture. Among the different structural elements embedded in their carboskeleton, the methanoquinolizidine system constitutes the signature structural element of this alkaloid family. Herein, we describe a novel synthetic access to this system which relies on a [2,3]-Stevens rearrangement and results in the formal synthesis of strictamine.
We report a concise and versatile total synthesis of the diterpenoid (+)‐norcembrene 5 from simple building blocks. Ring‐closing metathesis and an auxiliary‐directed 1,4‐addition are the key steps of our synthetic route. During the synthesis, an unprecedented, highly oxidized pentacyclic structural motif was established from a furanocembranoid through transannular [4+2] cycloaddition.
To date, more than 100 congeners of the akuammiline alkaloid family have been isolated. Their signature structural element is a methanoquinolizidine moiety, a cage-like scaffold structurally related to adamantane. The structural variations of the family members originate from oxidative processes that mostly trigger rearrangements of the methanoquinolizidine motif. The family of the akuammiline alkaloids is best represented by strictamine. It bears the least functionalized carbon skeleton of all family members without lacking the signature structural motifs. Herein, we report the formal synthesis of strictamine through a Stevens [2,3]-sigmatropic rearrangement as a key step and the synthetic pitfalls related with its synthesis.
Eine enantioselektive Totalsynthese des Diterpenoids (+)‐Norcembren 5 ausgehend von einfachen, gut zugänglichen Bausteinen wird berichtet. Schlüsselschritte unserer Synthese sind eine Ringschluss‐Metathese und eine Auxiliar‐basierte enantioselektive 1,4‐Addition. Im Zuge dieser Synthese wurde ein hochoxygeniertes pentacyclisches Ringsystem etabliert, das in einer spontanen transannularen [4+2]‐Cycloaddition gebildet wurde.
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