Characterization and Synthesis of Eudistidine C, a Bioactive Marine Alkaloid with an Intriguing Molecular Scaffold

J Org Chem. 2016 Nov 18;81(22):10631-10640. doi: 10.1021/acs.joc.6b02380. Epub 2016 Nov 10.

Abstract

An extract of Eudistoma sp. provided eudistidine C (1), a heterocyclic alkaloid with a novel molecular framework. Eudistidine C (1) is a racemic natural product composed of a tetracyclic core structure further elaborated with a p-methoxyphenyl group and a phenol-substituted aminoimidazole moiety. This compound presented significant structure elucidation challenges due to the large number of heteroatoms and fully substituted carbons. These issues were mitigated by application of a new NMR pulse sequence (LR-HSQMBC) optimized to detect four- and five-bond heteronuclear correlations and the use of computer-assisted structure elucidation software. Synthesis of eudistidine C (1) was accomplished in high yield by treating eudistidine A (2) with 4(2-amino-1H-imidazol-5-yl)phenol (4) in DMSO. Synthesis of eudistidine C (1) confirmed the proposed structure and provided material for further biological characterization. Treatment of 2 with various nitrogen heterocycles and electron-rich arenes provided a series of analogues (5-10) of eudistidine C. Chiral-phase HPLC resolution of epimeric eudistidine C provided (+)-(R)-eudistidine C (1a) and (-)-(S)-eudistidine C (1b). The absolute configuration of these enantiomers was assigned by ECD analysis. (-)-(S)-Eudistidine C (1b) modestly inhibited interaction between the protein binding domains of HIF-1α and p300. Compounds 1, 2, and 6-10 exhibited significant antimalarial activity against Plasmodium falciparum.

Publication types

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

MeSH terms

  • Alkaloids / chemical synthesis*
  • Alkaloids / chemistry
  • Animals
  • Carbon-13 Magnetic Resonance Spectroscopy
  • Chromatography, High Pressure Liquid
  • Heterocyclic Compounds, 4 or More Rings / chemical synthesis*
  • Heterocyclic Compounds, 4 or More Rings / chemistry
  • Marine Biology*
  • Molecular Structure
  • Proton Magnetic Resonance Spectroscopy
  • Spectrometry, Mass, Electrospray Ionization
  • Urochordata / chemistry*

Substances

  • Alkaloids
  • Heterocyclic Compounds, 4 or More Rings
  • eudistidine C