Synthesis of macrocyclic natural products by catalyst-controlled stereoselective ring-closing metathesis

Stereoselective ring closure There are a large number of chemical transformations in which alkenes act as the reactants and/or products of the reaction. Perhaps the most widely utilized approach to synthesis of unsaturated large rings is catalytic ring-closing metathesis (RCM), but this reaction often proceeds with little control over alkene. Amir Hoveyda and colleagues have developed a method for highly efficient and stereoselective synthesis of macrocyclic alkenes by catalytic RCM. It involves catalytic Z-isomer-selective cross-metathesis reactions of terminal enol ethers, which have not been reported previously, and allylic amides, used previously only in E-isomer-selective processes. The effectiveness of the method is demonstrated by the stereoselective synthesis of anticancer agents epothilone C and nakadomarin A.