Sanyensin with an Unprecedented Architecture: An Effective Strategy from Discovery to Stereochemical Identification of Flexible Natural Products.

Under the guidance of genome mining combined with bioassay-coupled metabolomic analyses, an unprecedented macrodiolide sanyensin (1), with two flexible macrolides fused by the rigid oxabicyclo[3.3.1]nonane core, was isolated from the deep-sea-derived Streptomyces sp. OUCT16-30. The stereochemistry of 1 was established by NOEs (nuclear Overhauser effects), J-based configuration analysis, Marfey's analysis, and together with a newly introduced stereochemical study workflow, which greatly shortens the time to obtain correct conformations of flexible structures based on the NMR constraints, thus leading to reliable quantum chemical calculations to establish the absolute configurations. This workflow is expected to have broad applicability for elucidating the stereochemistry of flexible natural products. The macrodiolide framework of 1 is proposed to be formed through a biocatalytic cyclodimerization, followed by a series of nonenzymatic reactions. This work leads to new insights into the unexplored biosynthetic potential of deep-sea microbes and also provides a practical streamline for efficient mining of novel natural products, from discovery to stereochemical finalization.