Studies on Quinones. IX. Synthesis of Isochroman-5, 8-Diones

Synthesis and antimicrobial activity of pyranobenzoquinones related to the pyranonaphthoquinone antibiotics

The synthesis and antimicrobial activity of isochromane-type analogs of the pyranonaphthoquinone antibiotics are reported. Isochromane derivatives with (17a, b) and without (22a, b) a C-4 hydroxyl moiety and their corresponding quinones (19a and 23), were prepared. Both quinones exhibited antimicrobial activity against Staphylococcus aureus, Bacillus atrophaeus and Streptococcus agalactiae, while the related isochromanes were inactive. The results suggest that the quinone moiety is important for biological activity while the C-4 hydroxyl may not be essential.

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

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.