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Abstract The development of a convergent radical annulation strategy for the synthesis of complex terpenoids from sclareolide is disclosed. This approach employs a 1,3‐diradical synthon to enable rapid C‐ring annulation through inter‐ and intramolecular radical couplings, exemplified in the concise syntheses of serratene and cyclodammarane scaffolds from a common intermediate. Key features include a rapid alternating polarity (rAP) Kolbe electrolysis for onoceradiene assembly, a Co‐electrocatalytic metal‐catalyzed hydrogen atom transfer (MHAT) 7‐endo‐trig cycloisomerization─the first of its kind─to form the serratene core, and a tandem Fe‐mediated reductive olefin coupling/enolate alkylation cascade─also unprecedented─to forge the [4.3.1] propellane motif of cyclodammaranes with complete diastereocontrol over three contiguous quaternary centers. These routes, completed in 5–9 steps, maximize skeletal bond‐forming efficiency, feature unique radical cascades, and highlight the advantages of radical‐based disconnections in terpenoid synthesis. 

Abstract We offer a new biogenetic proposal for the origin of the complex alkaloid alstonlarsine A, through rearrangement of theStrychnosalkaloids alstolucines B and F. Further, we provide evidence of the chemical feasibility of this proposal in the facile conversion of synthetic alstolucines into alstonlarsine A through a short, efficient sequence ofN‐methylation, β‐elimination, and a cascade 1,7‐hydride shift/Mannich cyclization. We believe that this is the first biogenetic proposal involving the “tert‐amino effect”, a hydride‐shift‐based internal redox trigger of a Mannich cyclization. A further interesting feature of the cascade is that its stereochemical outcome most likely originates in conformational preferences during the hydride shift.