SEARCH

SEARCH BY CITATION

Keywords:

  • hydrogen bonds;
  • natural products;
  • spirofungins;
  • spiroketals;
  • total synthesis

Abstract

The stereoselective total synthesis of the spiroketal containing Streptomyces metabolite (−)-spirofungin A (1) is described. A key step involved a spiroketalisation controlled by an intramolecular H-bond which favoured the desired spiroketal 4 (13:1 ratio). The presence of the intramolecular H-bond in 4 is possibly due to a 1,5-alkyne–oxygen interaction. Other key steps include an efficient cross-metathesis to form the spiroketal precursor, a tin mediated syn-aldol reaction and a Stille cross-coupling reaction to create the C22[BOND]C23 bond. A final Wittig extension followed by deprotection gave (−)-spirofungin A (1).