Enantioselective Synthesis and Racemization of (−)-Sinoracutine

Giulio Volpin, Nynke A. Vepřek, Andreas B. Bellan, Dirk Trauner

Research output: Contribution to journalArticle

Abstract

Sinoracutine is a recently isolated alkaloid with unusual stereochemical and biological properties. It features an unprecedented tetracyclic 6/6/5/5 skeleton that bears an N-methylpyrrolidine ring fused to a cyclopentenone. Interestingly, both enantiomers of sinoracutine have been independently isolated from the same plant, yet the molecule does not appear to occur as a racemate. Here, we present a short synthesis of (−)-sinoracutine that relies on a highly diastereoselective Pauson–Khand reaction and a Mandai–Claisen reaction to install the quaternary stereocenter. Our work establishes the absolute configuration of the levorotatory isomer and suggests that the optical purity of sinoracutine varies in nature due to its gradual racemization. Experimental evidence supports this proposal, and a plausible mechanism for the racemization is provided.

Original languageEnglish (US)
Pages (from-to)897-901
Number of pages5
JournalAngewandte Chemie - International Edition
Volume56
Issue number3
DOIs
StatePublished - Jan 1 2017

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Keywords

  • Kornblum oxidation
  • Pauson–Khand reaction
  • alkaloids
  • asymmetric synthesis
  • sigmatropic rearrangement

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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