A formal total synthesis of the potent immunosuppressant FK506 (1) has been achieved via a concise construction of the Merck advanced intermediate (-)-2. Key features of the successful strategy include stereocontrolled sigma-bond installation of the trisubstituted olefin moieties and an efficient coupling of the C(24)-C(34) dithiane (-)-10 with the C(10)-C(23) alpha-silyloxy primary iodide (-)-9.