Epimeric Face-Selective Oxidations and Diastereodivergent Transannular Oxonium Ion Formation Fragmentations: Computational Modeling and Total Syntheses of 12-Epoxyobtusallene IV, 12-Epoxyobtusallene II, Obtusallene X, Marilzabicycloallene C, and Marilzabicycloallene D
作者： James Clarke , Karl J. Bonney , Muhammad Yaqoob , Savade Solanki , Henry S. Rzepa
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摘要: The total syntheses of 12-epoxyobtusallene IV, II, obtusallene X, marilzabicycloallene C, and D as halogenated C15-acetogenin 12-membered bicyclic tricyclic ether bromoallene-containing marine metabolites from Laurencia species are described. Two enantiomerically pure C4-epimeric dioxabicyclo[8.2.1]tridecenes were synthesized by E-selective ring-closing metathesis where their absolute stereochemistry was previously set via catalytic asymmetric homoallylic epoxidation elaborated regioselective epoxide-ring opening diastereoselective bromoetherification. Epimeric face-selective oxidation Δ12,13 olefins followed bromoallene installation allowed access to the oppositely configured 12,13-epoxides II IV. Subsequent exploration putative biomimetic oxonium ion formation–fragmentations reactions revealed diastereodivergent pathways giving C respectivel...
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