Isolation, characterization and structures of PA-46101 A and B

New antibiotics, PA-46101 A and B, were isolated from the culture broth of a Streptomycete. The molecular formulae of A and B were determined to be C52H70O18 and C61H86O22, -respectively, by elemental analyses, NMR and mass spectrometry. Their structures were elucidated by X-ray crystallography and NMR spectroscopy. These antibiotics are active in vitro against anaerobic Gram-positive and Gram-negative bacteria and also against a limited number of aerobic Gram-positive bacteria.