Next, we aimed to construct bicyclic triketone 4 in a Dieckmann-type cyclization of the highly substituted cy- clopentanone 11. Unfortunately, a variety of different conditions resulted in the formation of 13 (Scheme 3). To suppress decarboxylation, reduction of the ester to the corresponding aldehyde and subsequent aldol cyclization was attempted. When ester 12 was treated with DIBAL-H at -78 °C, overreduction to the primary alcohol was a major side reaction. By lowering the temperature to -100 °C, the corresponding aldehyde could be isolated in 70% yield. The subsequent intramolecular Mukaiyama aldol reaction with boron trifluoride etherate afforded a mixture of epimeric β-hydroxy ketones. 17 Oxidation of the crude mixture of both epimers with Dess-Martin periodinane (DMP) eventually gave triketone 4 in 62% yield over three steps (Scheme 3).