Natural product synthesis Cyanthiwigin

The DAAA has successfully been applied as a key step in the total synthesis of a number of natural products due to its ability to generate quaternary carbon centres enantioselectively. For example (-H)-dichroanone (81), [42] oxybutynin, [43] (-)-cyanthiwigin F (84) [44] and other examples (Scheme 4.22) [45, 46]. As alluded to above the DAAA has also been extended to the asymmetric synthesis of a-fluorinated cyclohexanones, an important class of compounds for medicinal chemistry [47]. 

PhiUips et al. designed the tandem RRM reaction of bicyclic compounds having two reactive sites in side chains to synthesize a tricyclic diterpenoid cyanthiwigin U 137, which is isolated from both fungal and marine sources (Scheme 24.35). The two-directional tandem ROM-RCM sequence of bicyclo[2.2.2]-octane 135 was catalyzed by [Ru]-II (20mol%) under the ethylene atmosphere, and transformations of tricyclic compound 136 completed a synthesis of this natural product in 17% overall yield in 12 steps. 

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