Synthesis of pyranonaphthoquinone antibiotics involving the phthalide annulation strategy

The synthesis of the pyranonaphthoquinone antibiotic pentalongin was performed using the phthalide annulation strategy. Annulation of the cyanophthalide onto 6H-pyran-3-one resulted in a hongconin analogue, which upon further elaboration was converted into the natural product. © Georg Thieme Verlag Stuttgart