Isolation, Enantioselective Total Synthesis and Structure Determination of the Anthrapyran Metabolite SS 43405-e

The first enantioselective total synthesis of the anthrapyran metabolite SS 43405‐e, isolated from a marine‐derived streptomycete, is described, which also allows the determination of the so far unknown absolute (R) configuration of the natural product. For the synthesis the bromoanthracene derivative 3 is lithiated and coupled with the enantiopure aldehyde (S)‐4 to give 9, which is oxidatively transformed into the corresponding anthraquinone 10 and further into the ketone 2. The final step is the cyclization of 2 under acidic conditions to give the desired antibiotic (S)‐1. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)