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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Total Synthesis of (-)-Preussochromone A
Marc Paul Beller1, Klaus Harms1, Ulrich Koert1
1Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, D-35032 Marburg, Germany.
Abstract:
An enantioselective total synthesis of the natural product (-)-preussochromone A is reported. The tricyclic thiopyrane skeleton could be assembled via Lewis acid-mediated cycloisomerization of a precursor with a 2-thiochromenone substructure and an α-ketoester moiety. The chromenone core was synthesized by cyclization of a dithioketene acetal and oxidation to a 2-sulfonylchromenone to set up the subsequent thia-Michael-retro-Michael addition of an aliphatic thiol producing the highly oxidized side chain.
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