Macrocyclization using enyne metathesis

M. Shair and co-workers were the first to apply the enyne metathesis for macrocyclization during the biomimetic synthesis of (-)-longithorone A." The two 16-membered paracyclophane building blocks, one diene and one dienophile component, were prepared using 50 mol% Grubbs s first-generation catalyst under 1 atm ethylene gas pressure. These components, after several additional steps, underwent two facile Diels-Alder cycloaddition reactions to afford the natural product. 

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