Synthesis of analogues of griseusin A

[GRAPHICS] The synthesis of pyranonaphthoquinone-spiroacetals (3 and 4), which are syn thetic analogues of the pyranonaphthoquinone antibiotic griseusin A (1) is reported. The oxygenated substituents on the spiroacetal ring were introduc ed onto the key naphthalene intermediate (5) using an anti asymmetric aldol reaction. The pyranonaphthoquinone skeleton was then assembled via furofur an annulation to naphthoquinone (22) to construct a furonaphthofuran ring f ollowed by oxidative rearrangement to the furonaphthopyran ring.