Recent applications of olefin ring-closing metathesis (RCM) in the synthesis of biologically important alkaloids, terpenoids, polyketides and other secondary metabolites.

With the commercial availability of well-defined ruthenium metathesis catalysts which combine high stability and broad functional group compatibility with undiminished activity, ring-closing metathesis (RCM) is now routinely integrated in the planning of natural product syntheses. Thus, ring sizes of practically any kind from five onward may be formed. The presence of heteroatoms such as oxygen and nitrogen is of minor importance. Ring-strain and the presence of additional double bonds may be overcome by judicious selection of conditions. A major drawback of macrocyclic RCM still is the lack of E/Z stereocontrol. Nevertheless, the current overview will demonstrate the overwhelming power and scope of RCM in the total synthesis of structurally demanding natural products.