Small structural alterations greatly influence the membrane affinity of lipophilic ligands: Membrane interactions of bafilomycin A1 and its desmethyl derivative bearing 19F-labeling.

Molecular behavior under bilayer membrane environments is one of the important research topics concerning how organic molecules exert their biological activities when interacting with cellular membranes. However, chemistry-based approaches to this property have not been successful when compared with the structural biological strategy on ligand-receptor interactions. Here, we investigated the molecular behavior of the lipophilic ATPase inhibitor bafilomycin A1 and its derivatives under a lipid environment from a chemical point of view. Our results revealed significant differences in membrane affinity and dynamics among ligands having different inhibitory potencies, suggesting the specific contribution of ligand-membrane interactions to their biological activity.

Highly regioselective gold-catalyzed formal hydration of propargylic gem-difluorides.

Herein, we report a highly regioselective gold-catalyzed formal hydration of propargylic gem-difluorides. Not only does this transformation provide access to versatile fluorinated building blocks that were difficult or hardly possible to access beforehand, but it also represents a rare case of a highly regioselective gold-catalyzed hydroalkoxylation of internal alkynes and puts forward the utility of the difluoromethylene unit as a directing group in catalysis.

Modification of bafilomycin structure to efficiently synthesize solid-state NMR probes that selectively bind to vacuolar-type ATPase.

Bafilomycin (Baf) is one of the most potent inhibitors of vacuolar-type ATPase, which is strongly implicated in age-related diseases. However, the binding site of the antibiotic on the protein remains unclear because of the complexity of the structure of Baf bound to the target subunit in the transmembrane region. For conducting structural studies by applying solid-state NMR, which is one of the most promising methodologies available for structural analysis in membrane system, preparing bioactive fluorinated Baf analogues is essential. In this study two Baf analogues were carefully designed and efficiently synthesized through the convergent coupling of three segments. Biological evaluation revealed that the activity of 24-F-Baf was comparable to that of Baf, indicating its utility as a potential probe for solid-state NMR analysis. By contrast, desmethylated 24-F-Baf exhibited markedly diminished activity. The absence of two methyl groups caused a critical conformational change in the macrocyclic core structure necessary for binding to the target protein.