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Enantioselective Total Synthesis of (+)-Euphorikanin A

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journal contribution
posted on 2021-05-27, 21:44 authored by Moritz J. Classen, Markus N. A. Böcker, Remo Roth, Willi M. Amberg, Erick M. Carreira
We disclose the first total synthesis of (+)-euphorikanin A, an ingenane-derived natural product featuring an unprecedented 5/6/7/3-fused tetracyclic skeleton. Key to the approach is a SmI2-mediated ketyl–enoate reaction that leads to the formation of two rings in a single step. The polarity-reversed cyclization proceeds in excellent yield and high diastereoselectivity. Access to ring B is effected late in the synthesis by implementation of a number of chemoselective transformations, including in situ generation of a vinyl lithium species and subsequent intramolecular attack onto an α-ketolactone.