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)