Synthesis of a Spirovetivane Synthon1

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Abstract
The spirovetivane sesquiterpenes are characterized by a spiro [4,5]decane ring system. Illustrative are the essential oil component β-betiv ne (1) and the antifungal metabolite lubimin (2).2 As part of a structural problem arising from our investigations of plant anticancer constituents1 we developed a synthesis of the potential spirovetivane synthon 10. The very workable synthesis (5 → 10) of ketone 10 described below should prove useful in approaches to certain spirovetivanes with a 1,4 oxygen-carbon to spiro-carbon relationship. Initially efforts were directed at utilizing the Plattner3 malonic ester and Dieckmann cyclization4 approach (3 → 4) to ketone 7. The Singh4 route to ester 4 proved useful but selective decarboxylation to ketone 7 was unsatisfactory. The known5 rhodium on aluminum oxide catalyzed hydrogenation of ethyl p-hydroxy-benzoate followed by oxidation to ketone 7 proved to be very practical and further efforts to satisfactorily decarboxylate ester 4 were discontinued.