Concise Synthesis of (S,S)-(+)-Dehydrohomoancepsenolide

A concise total synthesis of the bis-butenolide 3 in optically active form is reported. Key steps are a zinc-mediated “three-component coupling” with formation of dienyne 9 which undergoes ring closing metathesis (RCM) on treatment with (PCy₃)₂Cl₂Ru=CHPh. Dimerization of the resulting butenolide 11 is then achieved via alkyne metathesis using (tBuO)₃WΞCCMe₃ as the catalyst. A Lindlar reduction completes this synthesis which delivers product 3 in only five steps with an overall yield of 25%