Synthesis of highly oxygenated benzo[j]fluoranthenes

The fluoranthene carbon skeleton with annelated rings is of interest for different areas of chemistry, including natural products, medicinal chemistry and material science for organic electronics as well as sensing. A number of polyketide-derived fungal metabolites, mostly from xylariaceous fungi, possess a differently oxygenated and/or reduced benzo[j]fluoranthene nucleus. Examples are bulgarein, bulgarhodin, hortein, daldinones A-D, truncatone, hypoxylonols A,B, xylarenol and benzo[j]fluoranthene-4,9-diol (1), recently isolated by Tan and coworkers (1) as one of the metabolites of Mantis-associated Daldinia eschscholzii fungus. Some of these compounds exhibit biological activity, e.g. topoisomerase I inhibition for bulgarein, cytotoxicity for daldinone C and D, immunosuppressive activity for 1 and tyrosine kinase inhibition for other compounds. To the best of our knowledge, no attempt to synthesize any of these compounds has been reported in the literature so far. We have developed a rapid and efficient pathway to prepare oxygenated benzo[j]fluoranthene natural compounds as well as synthetic derivatives. Following this procedure, the first total synthesis of benzo[j]fluoranthene-4,9-diol 1 and analogues was carried out .