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The tricyclic scaffold of the bacterial polyketide enterocin was recently shown to undergo stereodiversification through a series of abiotic isomerizations, described metaphorically as a "ballet of isomers". However, some confusion remains regarding the exact nature of these interconversions, with two independent reports proposing different reaction mechanisms and intermediates. Herein, we have rechoreographed enterocin's ballet of isomers to provide a unified mechanism and revised the structures reported for enterocins C, D, and F.

Stereodivergence in Nature encapsulates both enzymatic (biosynthetic) and non-enzymatic (chemical) diversification of natural product scaffolds arising from a single biosynthetic pathway. Herein, we report a fascinating example of stereodivergence for the bacterial polyketide enterocin, which we observed to undergo a series of facile skeletal rearrangements in solution, leading to four distinct isomeric structures. The final distribution of the four isomers was found to be highly sensitive to the conditions used, including solvent, temperature and pH. In this study, we have investigated the kinetics of these isomeric conversions, and using a combination of DFT and thermochemical calculations, were able to establish a mechanism detailing a concerted rearrangement and an unusual "gymnastic" sequence of pseudo-chair-boat conformational interconversions. In addition to these kinetic and mechanistic studies, we also performed a semisynthetic study aimed at stabilising the enterocin scaffold. In total, seven analogues of enterocin were synthesised and investigated for their stability and in vitro activity against a panel of bacteria, fungi, plants and mammalian cells.

Streptomyces sp. MST-91080 was isolated from a soil sample collected in Queensland, Australia. From this strain, yeppoonic acids A - D were purified and spectroscopically characterised. The yeppoonic acids are a family of diene enecarboxylic acids on a 1,2,4-trisubstituted benzene scaffold, structurally related to other Streptomyces secondary metabolites MF-EA-705α/β, NFAT-133 and the lorneic acids. Yeppoonic acids B and C show strong cytotoxicity against the NS-1 mouse myeloma cell line (IC