Synthetic studies on antascomicin A: construction of the C18–C34 fragment

Stereoselective synthesis of the C18–C34 fragment of antascomicin A is described. Construction of the C27–C34 carbocycle moiety was achieved via catalytic Ferrier carbocylization and Johnson–Claisen rearrangement, which was converted to iodide by use of asymmetric alkylation and Sharpless epoxidation as key transformations. Coupling of iodide and sulfone furnished the C18–C34 fragment.