Acid chlorides with indole Grignard reagents

Kutney s approach started with isophorone 84, which was converted into the dibenzoate 85, and thence to the acid 86 on treatment with indolyhnagnesium iodide. Conversion to the acid chloride followed by treatment with indolylmagnesium iodide, induced cyclization to the trans-taseA tetracycle 87. Base-catalyzed epimerization to the cM-fused tetracyclic ketone 88, followed successively by hydride reduction, conversion into the benzoate, treatment with the indole Grignard reagent, and deprotection, gave YCK (73) (Scheme 4). The overall yield was however low (4%), but the method allows access to 6a-c z-YCK via the ketone 87 (57,55). 

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