Synthesis and antibiotic activity of the tricyclic furo[3,2-c] isochromen-2-trione unit of the pyranonaphthoquinones.

ABSTRACT

The elaboration and biological activity of 15, containing the proposed pharmacophore for the antibiotic activity of the pyranonaphthoquinones, are reported. The synthetic strategy involved acid-catalyzed lactonization of mandelate 17 for isochroman ring formation, in combination with a Wittig-oxa-Michael functionalization of isochroman-3-ol derivative 20, a lactonization involving configurational inversion of a benzylic alcohol and a final AgO oxidation. Compound 15 showed activity against Staphylococcus aureus and Bacillus subtilis with MIC of 64 and 32 microg/mL, respectively.