Bidirectional Synthesis of the IJK Fragment of Ciguatoxin CTX3C by Sequential Double Ring-Closing Metathesis and Tsuji–Trost Allylation

[Image: see text] A novel four-step bidirectional strategy has been used to synthesize the IJK fragment of the marine polyether natural product CTX3C from a simple monocyclic precursor in a concise and efficient manner. The four-step bidirectional sequence involves ring-closing metathesis, alcohol oxidation, enol carbonate formation, and palladium-mediated Tsuji–Trost allylation.