Ciguatoxin, ring-closing metathesis

Construction of fused polycyclic ethers (particularly, ciguatoxins and gambieric acids) by strategies involving ring-closing metathesis 06CC3571. 

Clark s group also reported on ring-closing enyne metathesis for the preparation of six- and seven-membered cyclic enol ethers 428 n= 1,2) as potential building blocks for the synthesis of marine polyether natural compounds such as brevetoxins and ciguatoxins. Metathesis products 428 were obtained from ene-ynes 427 in 72-98% yield when the NHC-bearing catalyst C was used (Scheme 84) [179]. 

The ring-closing enyne metathesis has been used for the synthesis of alkenyl substituted six- and seven-membered cyclic enol ethers (Eq. 88) [144]. The reaction has been proposed as an element of the strategy for preparation of subunits of brevetoxins and ciguatoxins. 

The EF-ring of ciguatoxin 3C has been stereoselectively synthesized by iterative use of a cyclic ether formation process based on chirality-transferring Ireland-Claisen rearrangement and ring-closing alkene metathesis (Scheme 21). ... 

Goto, A., Fujiwara, K., Kawai, H., and Suzuki, T. (2007) Synthesis of the EF-ring of ciguatoxin 3C based on the [2,3]-Wittig rearrangement and ring-closing olefin metathesis. Org. Lett., 9, 5373-5376. 

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