The triumph of zinc: A short and highly efficient synthesis of the calyculin C-1-C-9 tetraene building block by Negishi coupling

A short and highly efficient synthesis of phosphonate 5, a key building blo ck of the C-1-C-9 tetraene fragment of calyculins and calyculinamides, has been achieved. The key step involves a novel, highly chemoselective Negishi coupling with a bismetallic reagent 13.