Ester dienolate [2,3]-Wittig rearrangement in natural product synthesis: diastereoselective total synthesis of the triester of viridiofungin A, A2, and A4

J Org Chem. 2005 Jul 8;70(14):5579-91. doi: 10.1021/jo0505270.

Abstract

[structure: see text] An ester dienolate [2,3]-Wittig rearrangement was utilized to access the alkylated citric acid skeleton 6 that is characteristic for the viridiofungins and other members of the alkyl citrate family of secondary natural products. The [2,3]-sigmatropic rearrangement of (Z,Z)-15 provided the rearrangement product (+/-)-syn-16 in moderate yield and with very good diastereoselectivity. A Julia-Kocienski olefination efficiently served to connect the polar head (+/-)-syn-26 with the lipophilic tail (32a-c) of the viridiofungins. Amide formation between the racemic viridiofungin precursors 35a-c and the enantiomerically pure amino acid L-tyrosine methyl ester followed by preparative reversed-phase HPLC provided the isopropyl dimethyl ester of viridiofungin A ((+)-39a), A2 ((+)-39b), and A4 ((+)-39c) as well as the nonnatural diastereomers (-)-38a-c.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkadienes / chemistry*
  • Bacterial Toxins / chemical synthesis*
  • Chromatography, High Pressure Liquid
  • Citrates / chemical synthesis*
  • Esters / chemistry
  • Molecular Structure
  • Stereoisomerism
  • Tyrosine / analogs & derivatives*
  • Tyrosine / chemical synthesis

Substances

  • Alkadienes
  • Bacterial Toxins
  • Citrates
  • Esters
  • pinnamine
  • viridiofungin A
  • Tyrosine