APPROACHES TO A KEY LACTONE INTERMEDIATE REQUIRED FOR THE SYNTHESIS OF PYRANONAPHTHOQUINONE ANTIBIOTICS

Addition of 2-trimethylsilyloxyfuran (19) to naphthoquinone (20) gave in 91% yield the furo[3,2-b]naphtho[2,1-d]furan (18) which upon treatment with ceric ammonium nitrate gave the hydroxy ester (24) in 70% yield. Attempts to induce an intramolecular transesterification of hydroxy ester (24) to bislactone (6), a key intermediate required for the synthesis of several pyranonaphthoquinone antibiotics, were unsuccessful. Hydroxy ester (24), however, is closely related to the antibiotic juglomycin (32).