Enantioselective formal synthesis of (+)-dihydrocorynantheine and (-)-dihydrocorynantheol

J Org Chem. 2009 Feb 6;74(3):1205-11. doi: 10.1021/jo802387c.

Abstract

The enantioselective construction of the 3-ethylindolo[2,3-a]quinolizidine moiety present in numerous indole alkaloids is reported, the key steps being a stereoselective cyclocondensation of (S)-tryptophanol with an appropriate racemic delta-oxoester and a regio- and stereoselective cyclization of the resulting oxazolopiperidones on the lactam carbonyl group. A new procedure for the removal of the hydroxymethyl auxiliary group, involving oxidation to an aldehyde, dehydration of the corresponding oxime, and reductive decyanation of the resulting alpha-aminonitrile, has been developed. The preparation of indoloquinolizidine 27 represents a formal total synthesis of (+)-dihydrocorynantheine, (-)-dihydrocorynantheol, and other indolo[2,3-a]quinolizidine and oxindole alkaloids bearing the same substitution pattern.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaloids / chemical synthesis*
  • Cyclization
  • Indoles / chemical synthesis
  • Piperidones / chemical synthesis
  • Piperidones / chemistry
  • Quinolizidines / chemical synthesis
  • Stereoisomerism
  • Tryptophan / analogs & derivatives
  • Tryptophan / chemistry

Substances

  • Alkaloids
  • Indoles
  • Piperidones
  • Quinolizidines
  • dihydrocorynantheol
  • tryptophanol
  • Tryptophan
  • hirsutine