Abstract
Direct transfer of protons and electrons between two tandem reactions is still a great challenge, because overall reaction kinetics is seriously affected by diffusion rate of the proton and electron carriers. We herein report a host–guest supramolecular strategy based on the incorporation of NADH mimics onto the surface of a metal-organic capsule to encapsulate flavin analogues for catalytic biomimetic monooxygenations in conjunction with enzymes. Coupling an artificial catalysis and a natural enzymatic catalysis in the pocket of an enzyme, this host–guest catalyst–enzyme system allows direct proton and electron transport between two catalytic processes via NADH mimics for the monooxygenation of both cyclobutanones and thioethers. This host–guest approach, which involves the direct coupling of abiotic and biotic catalysts via a NADH-containing host, is quite promising compared to normal catalyst–enzyme systems, as it offers the key advantages of supramolecular catalysis in integrated chemical and biological synthetic sequences.
Highlights
Direct transfer of protons and electrons between two tandem reactions is still a great challenge, because overall reaction kinetics is seriously affected by diffusion rate of the proton and electron carriers
Flavin-dependent enzymes, which are ubiquitous in nature, provide sufficient activation to insert oxygen into substrates with definite reaction mechanism that involves the reduction of flavin adenine dinucleotide (FAD) by NADH to yield a reduced FADH2 and an interaction between a rapidly formed peroxo species, FAD-OOH and the substrate[27,28,29]; we hypothesize that the supramolecular catalytic system with the NADH-modified capsule should be applicable for simulating flavin-dependent enzymes with different enzymes attributed to its inherent host–guest behavior
A ligand (H2ZPA) containing a dihydropyridine amido (DHPA) mimic similar to the active site of an NADH model with a pendant C(O)–NH group as potential hydrogen-bonding sites was synthesized by the Schiff base reaction of 2-formylpyridine and 4-(3,5-di(hydrazine-carbonyl)-4-phenyl-pyridin-1(4H)-yl)N-methyl-benzamide in ethanol (Supplementary Fig. 1)
Summary
Direct transfer of protons and electrons between two tandem reactions is still a great challenge, because overall reaction kinetics is seriously affected by diffusion rate of the proton and electron carriers. Coupling an artificial catalysis and a natural enzymatic catalysis in the pocket of an enzyme, this host–guest catalyst–enzyme system allows direct proton and electron transport between two catalytic processes via NADH mimics for the monooxygenation of both cyclobutanones and thioethers This host–guest approach, which involves the direct coupling of abiotic and biotic catalysts via a NADH-containing host, is quite promising compared to normal catalyst–enzyme systems, as it offers the key advantages of supramolecular catalysis in integrated chemical and biological synthetic sequences. 10 Å) and stabilize the reaction intermediates through supramolecular forces[30,31], the supramolecular systems that enforced cofactor, catalyst and substrate together would be beneficial to the effective biomimetic transformations[32,33] This promising approach for coupling the artificial enzyme and the natural enzyme into one pocket of the enzyme would allow direct proton and electron transport between the two enzymatic processes through the proton and electron transport channels via NADH mimics (Fig. 1). The ingenious design of host–guest supramolecular system well-controls the multiple electron transfer process during catalysis, allowing the tandem reaction to occur smoothly with high efficiency and selectivity even under a low intensity light (3 W household fluorescent lamp), which offers the key advantages of supramolecular catalysis in integrated chemical and biological synthetic sequences
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