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Total Synthesis of (+)-Crotogoudin

Authors


  • We are grateful to Dr. B. Schweizer, Dr. N. Trapp, and M. Solar for X-ray crystallographic analysis, to Dr. M.-O. Ebert, R. Arnold, R. Frankenstein, and P. Zumbrunnen for NMR measurements and ETH 15-10-2 for financial support. S.B. acknowledges the Stipendienfond Schweizerische Chemische Industrie (SSCI).

Abstract

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Fellowship of the ring: The first total synthesis of (+)-crotogoudin, a 3,4-seco-atisane diterpenoid natural product, is reported. Asymmetric access to the bicyclo[2.2.2]octane core is achieved through a desymmetrization of a meso-diketone with baker's yeast (LG=leaving group, PG=protecting group). A SmI2-induced radical cyclopropane-opening/annulation/elimination cascade affords the suitably decorated tetracyclic structure of (+)-crotogoudin. The synthesis led to revision of the reported optical rotation of the natural product and to assignment of its absolute configuration as an ent-atisane (5R,10R).

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