Homodimericin A: A Complex Hexacyclic Fungal Metabolite.

Microbes sense and respond to their environment with small molecules, and discovering these molecules and identifying their functions informs chemistry, biology, and medicine. As part of a study of molecular exchanges between termite-associated actinobacteria and pathogenic fungi, we uncovered a remarkable fungal metabolite, homodimericin A, which is strongly upregulated by the bacterial metabolite bafilomycin C1. Homodimericin A is a hexacyclic polyketide with a carbon backbone containing eight contiguous stereogenic carbons in a C20 hexacyclic core. Only half of its carbon atoms have an attached hydrogen, which presented a significant challenge for NMR-based structural analysis. In spite of its microbial production and rich stereochemistry, homodimericin A occurs naturally as a racemic mixture. A plausible nonenzymatic reaction cascade leading from two identical achiral monomers to homodimericin A is presented, and homodimericin A's formation by this path, a six-electron oxidation, could be a response to oxidative stress triggered by bafilomycin C1.

Selective activation of lanthanide luminescence with triarylboron-functionalized ligands and visual fluoride indicators.

Two triarylboron-functionalized carboxylate ligands have been found to be highly effective in selective activation of Tb(III) and Eu(III) emission and enable the use of the Tb(III) and Eu(III) complexes as highly effective luminescent indicators for F(-) and CN(-) in solution and on a solid substrate.