Juanlimycins A and B, Ansamycin Macrodilactams from <i>Streptomyces</i> sp.

Ansamycins are a family of macrolactams characterized by an aromatic chromophore with an aliphatic chain (<i>ansa</i> chain) connected back to a nonadjacent position through an amide bond. This family has shown a high degree of druggability exemplified by rifamycins, maytansinoids, and geldanamycins. In this study, the isolation of two novel ansamycin macrodilactams with unprecedented features, juanlimycins A (<b>1</b>) and B (<b>2</b>), from <i>Streptomyces</i> sp. LC6 were reported. The structures of <b>1</b> and <b>2</b> were assigned on the basis of analysis of NMR spectroscopic data and X-ray single crystal diffraction