Total Synthesis of Lehualide B by Allylic Alcohol-Alkyne Reductive Cross-Coupling

The total synthesis of anticancer marine natural product lehualide B is described. Overall, the synthesis proceeds in just eight steps from a simple gamma-pyrone, does not require the use of protecting groups, and delivers each nonconjugated trisubstituted alkene with high levels of stereoselection. The challenging C12-C16 bis-trisubstituted 1,4-diene was installed with a complex reductive cross-coupling reaction between a preformed Ti-allyne complex and a pyrone-containing allylic alcohol.