Total synthesis of (+)-clavilactone A and (-)-clavilactone B by ring-opening/ring-closing metathesis.

The enantioselective total synthesis of natural enantiomers of clavilactones A and B has been achieved. A key feature of the synthesis is the use of a ring-opening/ring-closing metathesis, which allows the one-pot transformation of a strained cyclobutenecarboxylate into a γ-butenolide.