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Keywords:

  • Total synthesis;
  • Medicinal chemistry;
  • Natural products;
  • Alkaloids;
  • Melanophryniscus klappenbachi;
  • Melanophryniscus cupreuscapularis

Abstract

The first total synthesis of the 3,5-disubstituted indolizidine toad alkaloid 239Q from the known pyrrolidine 1 has been achieved, in seven steps with a 35 % overall yield. The relative stereochemistry of natural 239Q was determined unambiguously by comparison of GC-FTIR spectra of synthetic material with the skin extracts of the toad Melanophryniscus cupreuscapularis. The C7 congeners at the 5-position (12 and 13) showed strong antagonist activities on the α4β2 nicotinic acetylcholine receptors.