Bicyclo[1.1.0]butanes are highly strained molecules that have recently attracted attention as versatile synthetic building blocks. In this study, the authors report that bicyclo[1.1.0]butylamides undergo a metal-free aerobic transformation with molecular oxygen to afford oxazolidin-4-ones via complete ring cleavage of the BCB framework. The reaction proceeds under mild conditions without any catalyst or photosensitizer, enabling efficient construction of heterocyclic scaffolds from readily accessible substrates. Control experiments with radical scavengers indicate the involvement of radical intermediates. This transformation expands the oxidative reactivity of BCB derivatives and provides a new entry to nitrogen-containing heterocycles from strained carbocyclic frameworks.

Arylbenziodoxaboroles, the pseudocyclic aryliodonium salts with boronate group in ortho position, can serve as unique benzyne precursors that can generate aryne species at room temperature in the presence of water or weak bases. In the present study, the authors investigated reactions of pseudocyclic arylbenziodoxaboroles with compounds containing group 15 elements: nitrogen, phosphorus, arsenic, and antimony. As a result, the authors developed a synthetic procedure that efficiently yields the corresponding onium salts under aqueous or weakly basic conditions. Furthermore, the structures of several products were established by X-ray crystallographic analysis. This new reaction can be used as an efficient synthetic method for preparation of quaternary ammonium, phosphonium, arsonium and stibonium salts.

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The authors investigated secondary metabolites produced by the fungus Chaetomium brasiliense NBRC 6548 and isolated a new depsidone, mollicellin Z2 (1), together with three known congeners, mollicellins D, H, and I (2–4). Spectroscopic analyses including 1D and 2D NMR and HREIMS established the structure of 1. This compound represents the first 4-desmethyl mollicellin analogue bearing a prenyl substituent at C-7, filling the previously unoccupied category in the structural classification of mollicellins. Biosynthetic considerations suggest that 1 is generated through a pathway distinct from those of known analogues. The isolated compounds exhibited antibacterial activity against Staphylococcus aureus and nontuberculous mycobacteria.

Rutin is a polyphenol with strong antioxidant activity that can protect the skin from oxidative stress caused by UV exposure. However, its poor solubility in oil-based carriers suitable for topical formulations limits its transdermal delivery. The authors developed a microemulsion (ME) incorporating deep eutectic solvents and surface-active ionic liquids (SAIL) to enhance the solubility and skin permeability of rutin. Structural characterization revealed nanostructures that depend on the alkyl chain length of the SAIL. MEs containing SAILs with shorter alkyl chains significantly improved the skin permeability of rutin compared with conventional formulations, demonstrating their potential as promising transdermal drug carriers.