Chemo‐ and Regioselective Dihydroxylation of Benzene to Hydroquinone Enabled by Engineered Cytochrome P450 Monooxygenase

Hydroquinone (HQ) is produced commercially from benzene by multi‐step Hock‐type processes with equivalent amounts of acetone as side‐product. We describe an efficient biocatalytic alternative using the cytochrome P450‐BM3 monooxygenase. Since the wildtype enzyme does not accept benzene, a semi‐rational protein engineering strategy was developed. Highly active mutants were obtained which transform benzene in a one‐pot sequence first into phenol and then regioselectively into HQ without any overoxidation. A computational study shows that the chemoselective oxidation of phenol by the P450‐BM3 variant A82F/A328F leads to the regioselective formation of an epoxide intermediate at the C3=C4 double bond, which departs from the binding pocket and then undergoes fragmentation in aqueous medium with exclusive formation of HQ. As a practical application, an E. coli designer cell system was constructed, which enables the cascade transformation of benzene into the natural product arbutin, which has anti‐inflammatory and anti‐bacterial activities.     

Nanozyme‐Catalyzed Cascade Reactions for Mitochondria‐Mimicking Oxidative Phosphorylation

Multiple‐enzyme‐involving cascade reactions that yield bioenergy are necessary in natural oxidative phosphorylation. However, in vitro applications are hampered by the sensitivity of catalytic activity to environmental adaptation. Herein, we explore nanozyme‐catalyzed cascade reactions in an assembled hybrid architecture for mitochondria‐mimicking oxidative phosphorylation. Hollow silica microspheres containing trapped gold nanoparticles were synthesized to promote two enzyme‐like catalytic reactions that transform glucose into gluconic acid in the presence of oxygen. The resulting transmembrane proton gradient drives natural ATP synthase reconstituted on the surface to convert ADP and inorganic phosphate into ATP. The assembled architecture possesses high activity for oxidative phosphorylation, comparable to that of natural mitochondria. This study provides a new natural–artificial hybrid prototype for exploring bioenergy supply systems and holds great promise for ATP‐powered bioapplications.     

Catalytic Generation of C1 Ammonium Enolates from Halides and CO for Asymmetric Cascade Reactions

A general strategy for the design of asymmetric cascade reactions using readily available halides and carbon monoxide (CO) as substrates is developed. The key is the catalytic generation of C1‐ammonium enolates for the subsequent asymmetric cascade reactions through the combination of palladium‐catalyzed carbonylation and chiral Lewis base catalysis. Utilizing this strategy, we have established asymmetric formal [1+1+4] and [1+1+2] reactions to afford chiral dihydropyridones and β‐lactams with high yields and high enantio‐ and diastereoselectivities.     

Stereochemical Dichotomy in Two Competing Cascade Processes: Total Syntheses of Both Enantiomers of Spiroxin A

The first total synthesis of the marine antibiotic spiroxin A has been achieved for both enantiomeric forms. The discovery of two competing cascade processes triggered by two orthogonal stimuli, photo‐irradiation or acid/base treatment, enabled the divergent conversion of a single chiral, nonracemic bis‐quinone into both enantiomers of an advanced intermediate en route to both (?)‐ and (+)‐spiroxin A. The mechanism of the enantiodivergence is discussed.     

Hydrogel-Immobilized Coacervate Droplets as Modular Microreactor Assemblies

Immobilization of compartmentalized microscale objects in 3D hydrogels provides a step towards the modular assembly of soft functional materials with tunable architectures and distributed functionalities. Herein, we report the use of a combination of micro-compartmentalization, immobilization, and modularization to fabricate and assemble hydrogel-based microreactor assemblies comprising millions of functionalized polysaccharide–polynucleotide coacervate droplets. The heterogeneous hydrogels can be structurally fused by interfacial crosslinking and coupled as input and output modules to implement a UV-induced photocatalytic/peroxidation nanoparticle/DNAzyme reaction cascade that generates a spatiotemporal fluorescence read-out depending on the droplet number density, intensity of photoenergization, and chemical flux. Our approach offers a route to heterogeneous hydrogels with endogenous reactivity and reconfigurable architecture, and provides a step towards the development of soft modular materials with programmable functionality.