Modular Metal-Quinone Networks with Tunable Architecture and Functionality

Nanostructured materials with tunable structures and functionality are of interest in diverse areas. Herein, metal ions are coordinated with quinones through metal-acetylacetone coordination bonds to generate a class of structurally tunable, universally adhesive, hydrophilic, and pH-degradable materials. A library of metal-quinone networks (MQNs) is produced from five model quinone ligands paired with nine metal ions, leading to the assembly of particles, tubes, capsules, and films. Importantly, MQNs show bidirectional pH-responsive disassembly in acidic and alkaline solutions, where the quinone ligands mediate the disassembly kinetics, enabling temporal and spatial control over the release of multiple components using multilayered MQNs. Leveraging this tunable release and the inherent medicinal properties of quinones, MQN prodrugs with a high drug loading (>89 wt %) are engineered using doxorubicin for anti-cancer therapy and shikonin for the inhibition of the main protease in the SARS-CoV-2 virus.

Stereoselective Total Synthesis of the Dimeric Naphthoquinonopyrano-γ-lactone (-)-Crisamicin A: Introducing the Dimerization Site by a Late-Stage Hartwig Borylation

The first stereoselective total synthesis of the dimeric naphthoquinonopyrano-γ-lactone (-)-crisamicin A was realized (13 steps, 5% overall yield). 1,4,5-Trimethoxynaphthalene, reached in five known steps, was brominated at C-3 to install a but-3-enoic ester by an ensuing Heck coupling. An asymmetric Sharpless dihydroxylation followed and gave a β-hydroxy-γ-lactone with >99.9% ee. Its OH substituent and acetaldehyde established the dihydropyran ring in a completely diastereoselective oxa-Pictet-Spengler cyclization. The 2,3-fused anisole moiety allowed the C⁵-H bond under Hartwig's conditions to be borylated. This set the stage for engaging the resulting C⁵-B bond in an oxidative dimerization, which led to a binaphthohydroquinon-5-yl. The latter was advanced to synthetic crisamicin A by a double CAN oxidation (→ a binaphthoquinon-5-yl) and a double demethylation.