[structure: see text] An enantioselective strategy to the spirocyclic core found in the oroidin-derived family of bisguanidine marine alkaloids has been devised, premised on a biosynthetic proposal. Herein, we describe the successful implementation of this strategy, which entails a Diels-Alder reaction and a chlorination/ring contraction sequence that delivers the fully functionalized spirocyclic core. In this initial report, an intermolecular chlorination delivers a cyclopentane that is epimeric at C17 relative to the palau'amines and epimeric at C11 relative to the axinellamines.
Enantioselective Strategy to the Spirocyclic Core of Palau'amine and Related Bisguanidine Marine Alkaloids.-A concise, enantioselective approach to the spirocyclic core of the bisguanidine family of marine natural products is developed. Key steps of the synthesis are a Diels-Alder reaction furnishing the tricyclic scaffold (III) and a chlorination/ring contraction sequence that delivers the spirocyclic core. Spirocycle (VII) possesses the full complement of cyclopentane functionality found in palauamine but is epimeric at the chlorine-bearing atom. -(DILLEY, ANJA S.; ROMO, DANIEL; Org. Lett. 3 (2001) 10, 1535-1538; Dep. Chem., Tex. A&M Univ., College Station, TX 77843, USA; EN)
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