Cc1cc(O)c2c3c(ccc2c1)C(=O)c1c(ccc([C@H]2C[C@H]4O[C@H]5CC(=O)[C@H](C)O[C@H]5O[C@@H]4[C@@H](C)O2)c1O)C3=O marangucycline B