Tigliane ring system

The transient intervention of a carbonyl ylids has culminated in numerous elegant approaches to total syntheses of natural products, such as the synthesis of the tigliane ring system (61-63) by Dauben [53] (Scheme 28). 

Dauben used a related cyclization-cycloaddition approach for the synthesis of tigliane 22. Carbonyl ylide 21, derived from the diazo ketoester 20, underwent intramolecular cycloaddition to form 22, a molecule which contains the C(6), C(9)-oxido bridge of the tigliane ring system (Scheme 5) (93JOC7635). 

Wender and coworkers had established a methodology for the synthesis of a family of simple tigliane-daphnane analogues, based on the zirconocene-me-diated enyne carbocyclization, demonstrating both the extension of the car-bocyclization methodology to cycloheptanoid synthesis and the control of stereochemistry from a pre-existing ring system with the zirconocene-medi-ated carbocyclization reaction (Eq. 45) [47]. 

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