Application of a stereospecific intramolecular allenylsilane imino ene reaction to enantioselective total synthesis of the 5,11- methanomorphanthridine class of Amaryllidaceae alkaloids

Jian Jin, Steven M. Weinreb

Research output: Contribution to journalArticle

76 Scopus citations

Abstract

Enantioselective total syntheses of the pentacyclic 5,11- methanomorphanthridine Amaryllidaceae alkaloids (-)-montanine (1), (-)- coccinine (2), and (-)-pancracine (3) were accomplished using an intramolecular concerted pericyclic allenylsilane imino erie cycloaddition as a key step. These complex natural products were constructed starting from readily available enantiomerically pure epoxy alcohol 15 which was converted to allenylsilane aldehyde 28 via an efficient nine-step sequence. The imine generated from aldehyde 28 and iminophosphorane 47 underwent a stereospecific thermal imino ene reaction to afford key intermediate cis aminoalkyne 49. It was possible to transform this compound via Lindlar hydrogenation followed by an intramolecular Heck reaction to seven-membered ring tetracycle 51, This olefinic intermediate could be fanctionalized through its epoxide to yield α-hydroxymethyl intermediate 54, and then pentacyclic alcohol 64. Procedures were then developed to convert this material to the enantiomerically pure alkaloids 1-3. A formal enantioselective total synthesis of (-)-brunsvigine (4) was also achieved via triol 72.

Original languageEnglish (US)
Pages (from-to)5773-5784
Number of pages12
JournalJournal of the American Chemical Society
Volume119
Issue number25
DOIs
StatePublished - Jan 1 1997

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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