Dimeric Pyranonaphthoquinones: Isolation, Bioactivity, and Synthetic Approaches

The dimeric pyranonaphthoquinones, bis versions of the naphtho[2,3-c]pyran-5,10-dione moiety, comprises a group of antibiotics that have been isolated from a variety of sources including plants, bacteria, fungi, and insects. This review discusses the known naturally occurring dimeric pyranonaphthoquinones, their isolation and bioactivity, and synthetic approaches towards them that have helped to confirm their structures, as well as to resolve structural uncertainties such as stereochemistry. The major focus has been on the synthetic approaches adopted to complete the challenging total synthesis of the natural isolates and analogues.