A VERSATILE INTERMEDIATE FOR THE SYNTHESIS OF PYRANOQUINONE ANTIBIOTICS

As a result of the sophisticated detection and isolation procedures developed by Omura1 and others, the family of biologically active pyranoquinones continues to grow rapidly. As a consequence of their interesting structures and useful activity, several synthetic approaches have already appeared.2 Its members include the antimyco-plasmal antibiotics frenolicin B (1)3 and nanaomycin A (2),4 the antifungal agent kalafungin (3),5 the antibiotics me-dermycin (4)6 and mederrhodin (5),7 and the novel C-glycoside SCH 38519 (6),8 which inhibits the growth of Gram-negative and Gram-positive microorganisms. It is clear from an examination of their structures depicted below that the primary difference lies in the substitution pattern on the naphthoquinone subunit. Since an acid such as 2 can be converted into a lactone in high yield under mild conditions,4 our interest in developing a common intermediate for the synthesis of all of these natural products led us to embark on the preparation of quinone 7, wherein X could be a phenylthio group or a bromide or chloride. © 1990, American Chemical Society. All rights reserved.