Total syntheses of the monoterpene indole alkaloids (±)-alstilobanine A and E and (±)-angustilodine

J Org Chem. 2014 Jan 3;79(1):7-24. doi: 10.1021/jo402495q. Epub 2013 Dec 12.

Abstract

A synthetic strategy has been developed culminating in stereoselective total syntheses of the small class of unusual monoterpenoid indole alkaloids exemplified by alstilobanines A (3) and E (2) and angustilodine (1). A pivotal step includes a novel intermolecular Michael-type addition of an indole ester dianion to a piperidine-derived nitrosoalkene to form the C15, C16 bond of the alkaloids. In addition, an application of the Romo protocol for effecting a stereoselective intramolecular nucleophile-assisted aldol-lactonization was employed, leading to a β-lactone incorporating the requisite cis-fused 2-azadecalin moiety and also setting the C15, C19, C20 relative stereochemistry of the metabolites. It was then possible to stereoselectively effect an aldolization of a dianion derived from this indole ester β-lactone intermediate with formaldehyde to introduce the requisite C16 hydroxymethyl group. Further manipulations of the system ultimately led to the three alkaloids in racemic form.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Molecular Structure
  • Secologanin Tryptamine Alkaloids / chemical synthesis*
  • Secologanin Tryptamine Alkaloids / chemistry
  • Stereoisomerism

Substances

  • Secologanin Tryptamine Alkaloids
  • alstilobanine A
  • alstilobanine E
  • angustilodine