Synthetic studies on macroviracin A: a rapid construction of C(42) macrocyclic dilactone corresponding to the core

The C(2)-symmetric macrodiolide core 2 of an antiviral agent, macroviracin A (1), was constructed in a single step by the intermolecular macrodimerization of C(22)-hydroxy carboxylic acid 3 with 2-chloro-1,3-dimethylimidazolinium chloride and DMAP in the presence of sodium hydride (NaH). The use of potassium hydride instead of NaH caused the intramolecular cyclization, predominantly providing the corresponding monomer 26. The acid 3 was synthesized through a series of reactions such as the coupling reaction of acetylene 5 and oxirane 6, stereoselective glycosidation with the trichloroacetimidate method, and Jones oxidation.