Dyotropic Rearrangements of Fused Tricyclic 尾-Lactones: Application to the Synthesis of (鈭?-Curcumanolide A and (鈭?-Curcumalactone

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• 作者：Carolyn A. Leverett ; Vikram C. Purohit ; Alex G. Johnson ; Rebecca L. Davis ; Dean J. Tantillo ; Daniel Romo
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：August 15, 2012
• 年：2012
• 卷：134
• 期：32
• 页码：13348-13356
• 全文大小：570K
• 年卷期：v.134,no.32(August 15, 2012)
• ISSN：1520-5126

文摘

Dyotropic rearrangements of fused, tricyclic 尾-lactones are described that proceed via unprecedented stereospecific, 1,2-acyl migrations delivering bridged, spiro-纬-butyrolactones. A unique example of this dyotropic process involves a fused bis-lactone possessing both 尾- and 未-lactone moieties which enabled rapid access to the core structures of curcumanolide A and curcumalactone. Our current mechanistic understanding of the latter dyotropic process, based on computational studies, is also described. Other key transformations in the described divergent syntheses of (鈭?-curcumanolide A and (鈭?-curcumalactone from a common intermediate (11 and 12 steps from 2-methyl-1,3-cyclopentanedione, respectively), include a catalytic, asymmetric nucleophile (Lewis base)-catalyzed aldol-lactonization (NCAL) leading to a tricyclic 尾-lactone, a Baeyer鈥揤illiger oxidation in the presence of a 尾-lactone, and highly facial-selective and stereocomplementary reductions of an intermediate spirocyclic enoate. The described dyotropic rearrangements significantly alter the topology of the starting tricyclic 尾-lactone, providing access to complex spirocyclic cyclopentyl-纬-lactones and bis-纬-lactones in a single synthetic operation.