Trichophycins B-F, Chlorovinylidene-Containing Polyketides Isolated from a Cyanobacterial Bloom

J Org Chem. 2018 Nov 2;83(21):13256-13266. doi: 10.1021/acs.joc.8b02070. Epub 2018 Oct 17.

Abstract

NMR-guided isolation (based on 1D 1H and 13C NMR resonances consistent with a chlorovinylidene moiety) resulted in the characterization of five new highly functionalized polyketides, trichophycins B-F (1-5), and one nonchlorinated metabolite tricholactone (6) from a collection of Trichodesmium bloom material from the Gulf of Mexico. The planar structures of 1-6 were determined using 1D and 2D NMR spectroscopy, mass spectrometry, and complementary spectroscopic procedures. Absolute configuration analysis of 1 and 2 were carried out by 1H NMR analysis of diastereomeric Mosher esters in addition to ECD spectroscopy, J-based configuration analysis, and DFT calculations. The absolute configurations of 3-6 were proposed on the basis of comparative analysis of 13C NMR chemical shifts, relative configurations, and optical rotation values to compounds 1 and 2. Compounds 1-5 represent new additions to the trichophycin family and are hallmarked by a chlorovinylidene moiety. These new trichophycins and tricholactone (1-6) feature intriguing variations with respect to putative biosynthetic starting units, halogenation, and terminations, and trichophycin E (4) features a rare alkynyl bromide functionality. The phenyl-containing trichophycins showed low cytotoxicity to neuro-2A cells, while the alkyne-containing trichophycins showed no toxicity.

Publication types

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

MeSH terms

  • Antineoplastic Agents / administration & dosage
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Dose-Response Relationship, Drug
  • Harmful Algal Bloom*
  • Humans
  • Molecular Structure
  • Polyketides / chemistry*
  • Trichodesmium / chemistry*

Substances

  • Antineoplastic Agents
  • Polyketides