An enzyme-based amperometrlc biosensor for hydrogen peroxide was developed, employing a horseradish peroxidase (HRP) monolayer covalently attached to a tin oxide electrode and a dissolved electron mediator. The sensor can determine hydrogen peroxide at levels down to 10~* M and can be applied to a flow system. Stability of the electrode, kinetics of the surface process, and the efficiencies of different mediators were studied. As an extension, glucose oxidase (GOx) was chemically bound to the HRP-modMed electrode. A GOx/HRP bilayer-modified electrode thus obtained exhibits much better performance in glucose detection limit, sensitivity, and response speed than previously reported GOx monolayer-modified electrodes.

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An efficient and convenient approach to the synthesis of spirocyclic oxindoles from iodoindoles involves a sequential intramolecular CO Ullmann coupling reaction and Claisen rearrangement (see scheme). The one‐pot procedure affords 3‐spiro‐2‐oxindoles in good yield with excellent diastereoselectivities.

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