AN UNPRECEDENTED RING EXPANSION IN THE MACROLIDE SERIES - SYNTHESIS OF ISO-BAFILOMYCIN A1

Article abstract of DOI:10.1016/S0040-4039(00)73508-8

When treated with a reagent prepared from equimolar quantities of methyllithium and copper iodide, 7,21-di-O-TMS bafilomycin A2 3 undergoes ring expansion to give the 18-membered lactone homolog 5 in nearly quantitative yield.Acid hydrolysis gives iso-bafilomycin A1.Ring contraction to the original 16-membered lactone takes place in the presence of fluoride ion.A mechanistic rationale and X-ray crystallographic evidence are presented.