Alpha,alpha'-annulation of 2,6-prenyl-substituted cyclohexanone derivatives with malonyl chloride: application to a short synthesis of (+/-)-clusianone. Formation and rearrangement of a biogenetic-like intermediate.

Conditions were found for the successful Effenberger alpha,alpha'-annulation of 3,3-dimethyl-2,4,6-triprenyl cyclohexanone silyl enol ethers with malonyl chloride to give the corresponding bicyclo[3.3.1]nonane-trione in 35% yield, this result allowing a short synthesis of (+/-)-clusianone. An isomeric rearranged bicyclo[3.3.1]nonane-trione was also isolated in 25% yield, and changing the Lewis acid resulted in formation of a lavandulyl-substituted phloroglucinol derivative in 38% yield. The mechanism of formation of these two last products mimics the biogenetic pathway to PPAPs. [reaction: see text]

Synthetic studies towards bridgehead diprenyl-substituted bicyclo[3.3.1]nonane-2,9-diones as models for polyprenylated acylphloroglucinol construction

The synthesis of bridgehead diprenylated bicyclo[3.3.1]-nonane-2,9-dione, based on a reductive rearrangement of an enol lactone, is presented. The same target could be reached by a one-step sequence involving Michael addition of 2,6-diprenylcyclohexanone onto acrolein and intramolecular aldol reaction. The first method could be extended to the formation of a compound with gem-dimethyl substituents adjacent to the bridgehead position, but the construction of a suitably substituted enol lactone, with a view to polyprenylated acylphloroglucinol elaboration, could not be achieved. © Wiley-VCH Verlag GmbH and Co. KGaA, 2007

New polycyclic diamine scaffolds from dimerization of 3-alkyl-1,4-dihydropyridines in acidic medium.

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simple and convenient method for the synthesis of 2-substituted glutaconaldehyde salts and 2-substituted glutaconaldehyde derivatives

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