<i>O</i>‑Alkylazoxymycins A–F, Naturally Occurring Azoxy-Aromatic Compounds from <i>Streptomyces</i> sp. Py50

Six new azoxy-aromatic compounds (o-alkylazoxymycins A–F, 1–6) and two new nitrogen-bearing phenylvaleric/phenylheptanoic acid derivatives (o-alkylphemycins A and B, 7 and 8) were isolated from Streptomyces sp. Py50. Their structures were elucidated based on HRESIMS, NMR, UV spectroscopic analyses, and X-ray crystallographic data. O-Alkylazoxymycins A–F (1–6) are the first natural examples of azoxy compounds with the azoxy bond attached to the ortho-position of the phenylheptanoic acid or phenylvaleric acid moiety. Compounds 1, 5, and 6 were active against Epidermophyton floccosum with MIC50 values ranging from 10.1 to 51.2 μM. A plausible biosynthetic pathway of 2 and 3 was proposed.