The homochiral lactone (5) and the oxazolidinone (9), together with the phosphonium salt (15), serve as key building blocks for the enantioselective synthesis of the (Z)-bis(silyloxy) ester (17), whose photochemical conversion into the (E)-isomer (18) constitutes a formal synthesis of the antifungal macrocyclic lactone (-)-gloeosporone (2).