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Abstract A metal–organic framework (MOF), ZIF‐8, which is stable at neutral and slightly basic pH values in aqueous solutions and destabilized/dissolved under acidic conditions, is loaded with a pH‐insensitive fluorescent dye, rhodamine‐B isothiocyanate, as a model payload species. Then, the MOF species are immobilized at an electrode surface. The local (interfacial) pH value is rapidly decreased by means of an electrochemically stimulated ascorbate oxidation at +0.4 V (Ag/AgCl/KCl). Oxygen reduction upon switching the applied potential to −0.8 V allows to return the local pH to the neutral/basic pH, then stopping rapidly the release process. The developed method allows electrochemical control over stimulated or inhibited payload release processes from the MOF. The pH variation proceeds in a thin film of the solution near the electrode surface. The switchable release process is realized in a buffer solution and undiluted human serum. As the second option, the pH decrease stimulating the release process is achieved upon an enzymatic reaction using esterase and ester substrate. This approach potentially allows the release activation controlled by numerous enzymes assembled in complex biocatalytic cascades. It is expected that related electrochemical or biocatalytic systems can represent novel signal‐responding materials with switchable features for delivering (bio)molecules within biomedical applications.
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Interfacing Whole Cell Biocatalysis with a Biocompatible Pictet‐Spengler Reaction for One‐Pot Syntheses of Tetrahydroisoquinolines and Tryptolines**
Abstract Biocatalytic processes are highly selective and specific. However, their utility is limited by the comparatively narrow scope of enzyme‐catalysed transformations. To expand product scope, we are developing biocompatible processes that combine biocatalytic reactions with chemo‐catalysis in single‐flask processes. Here, we show that a chemocatalysed Pictet‐Spengler annulation can be interfaced with biocatalysed alcohol oxidation. This two‐step, one‐pot cascade reaction converts tyramine and aliphatic alcohols to tetrahydroisoquinoline alkaloids in aqueous buffer at mild pH. Tryptamine derivatives are also efficiently converted to tryptolines. Optimization of stoichiometry, pH, reaction time, and whole‐cell catalyst deliver the tetrahydroisouinolines and tryptolines in >90 % and >40 % isolated yield, respectively, with excellent regioselectivity.
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- Award ID(s):
- 2138143
- PAR ID:
- 10493255
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- ChemBioChem
- Volume:
- 24
- Issue:
- 24
- ISSN:
- 1439-4227
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/cbic.202300464
