β-Ketoesters as Mono- or Bisnucleophiles: A Concise Enantioselective Total Synthesis of (-)-Englerin A and B
- PMID: 30938023
- DOI: 10.1002/anie.201900401
β-Ketoesters as Mono- or Bisnucleophiles: A Concise Enantioselective Total Synthesis of (-)-Englerin A and B
Abstract
A short enantioselective total synthesis of englerin A, a guaiane sesquiterpene with significant in vitro antitumor activity, is reported. Key features of this total synthesis are an organocatalytic asymmetric decarboxylative aldol reaction, a neighboring-group-participating [4+3] cycloaddition, a novel one-pot Heck coupling/regioselective 1,4-hydrosilylation/Tamao-Fleming oxidation cascade, and a kinetic CBS reduction, generating the optically pure natural product in 6.7 % overall yield over twelve steps starting from methylglyoxal. Selective saponification of the more reactive glycolic ester moiety of englerin A also gave (-)-englerin B.
Keywords: antitumor agents; asymmetric catalysis; natural products; organocatalysis; total synthesis.
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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